These are actions arising out of alleged medical malpractice. Defendants sought discovery of plaintiffs’ expert witnesses, medical treatises or articles relied on in support of liability and reports of the experts. On leave granted, defendants appeal from the trial court’s denial of discovery.
In order to determine precisely what is involved on this appeal and to limit decision to the questions before us, we detail the procedural steps below.
After appearance and before answer, defendants Stanley and Stringer filed demands for bills of particulars, which were furnished. After answers were filed by these defendants, they addressed written interrogatories to Donovan Klabunde or “his representatives who know the facts about which-inquiry is made”. The interrogatory pertinent to decision of this appeal read:
“State the name and address of every member of the medical profession that you have consulted or had conferences with, or your attorneys have had conferences with or consulted with as proposed expert witnesses to testify on your behalf as to the alleged negligence or malpractice of defendants.”
Plaintiffs’ answer read:
“I do not have sufficient knowledge to answer interrogatory III (the interrogatory quoted above) with reference to my attorneys, but as to myself, the answer is none.”
Individual defendants then filed a motion to compel answer to interrogatories or furnish identity of expert witnesses. Plaintiffs’ attorney filed an affidavit in opposition to this motion, and it was denied.
*493Although, current discovery rules, GCR 1963, chapter 30, changed the method for obtaining discovery from motion and court order to notice only, they did not alter the discretion of the trial judge to grant, deny or limit discovery. Court Rule No 35, § 6 (1945)1 and GCR 1963, 306.2 and 307.4. Presently, the discovery sought is obtained on notice, except as limited by protective order. Under GCR 1963, 306.2 and 307.4 and for good cause shown, the authority of the trial court in relation to discovery appears to be unlimited. This is as it should be. What discovery should be granted, denied or limited in a given case is peculiarly within the function of the trial judge, and his determination should not be disturbed on appeal absent a showing of abuse of discretion. Such abuse cannot be shown by a record which demonstrates the trial judge acted for good cause shown.
Before discussing the concept of good cause shown, we note that the discovery rules do not differentiate between witnesses and expert witnesses. We note that what defendants sought by discovery was within the language of GCR 1963, 302.1 and 302.2, and we further note that privilege and work product were not involved.
In reviewing a record to determine whether or not the trial judge acted for good cause shown in making an order relating to discovery, we must bear in mind that discovery rules must be accorded broad and liberal treatment. Wilson v. Saginaw Circuit Judge (1963), 370 Mich 404. Such rules were designed to simplify and clarify issues, and their pui-pose was to provide accurate information in advance of trial as to the actual facts and circumstances of a controversy rather than aid in their concealment. Ewer v. Dietrich (1956), 346 Mich 535.
*494The c&iisé shown for denial of discovery in this báfee consisted of statements by plaintiffs’ attorney in his affidavit that “obtaining of an expert witness to testify against a fellow practitioner is a matter of great difficulty and of considerable delicacy.” Plaintiffs’ attorney fears the medical witness will not testify if his name is disclosed because the medical witness informed deponent that the witness cannot practice medicine without malpractice insurance, and it was canceled once because he testified against a doctor in a malpractice action. If discovery is granted, it will give defendants no more information that they already possess, according to plaintiff.
This record does not demonstrate that denial of discovery was for good cause shown and the order of the trial court must be reversed.
These actions have not been tried, although they were filed nearly 7 years ago. We make no assessment of the fault for the delay; we note it. Generally, expert testimony is essential to the establishment of a cause of action for professional malpractice. Lince v. Monson (1961), 363 Mich 135. The weight and credibility of the expert’s testimony is directly dependent on his qualifications and experience in the field of his testimony. Adequate trial preparation requires an opportunity to investigate these qualifications and this experience.
These factors cause us to exercise our authority under GCR 1963, 820.1(7)2 and to provide for the entry of an order in this Court requiring plaintiffs to divulge the names and addresses of their proposed expert witnesses, restricting plaintiffs to the use at trial of those experts divulged, and authorizing defendants to depose such experts at defendants’ expense with respect to the qualifications and ex*495perience of the experts in the field of their testimony and whether such experts considered any facts not available to defendants in formulating their opinions. In the event the experts answer the last inquiry affirmatively, they may be deposed as to those facts. The order shall further provide that the time and place of the depositions shall be fixed by agreement of counsel or order of the trial court; the time to be such that the depositions are available for trial.
Reversed and remanded for further proceedings with costs to defendants.
McGregor, J., concurred.See 334 Mich xl.
As amended. See 373 Midi brix.