During a five-year period preceding July 1986, Bennett, an attorney, defended Crawford Long Hospital in eighteen malpractice complaints, for which he was compensated by the hospital’s insurer. Seventeen of these cases involved personal injuries alleged to be the result of negligent medical care, and at least six involved allegations of negligence regarding improper surgical procedures and postoperative care.

In 1984, while Bennett was representing the hospital in defense *721of malpractice claims, Yerby underwent back surgery at the hospital, and he died on the same day. In 1986, Bennett ceased representing the hospital, and later that year filed a complaint against the hospital on behalf of Yerby’s widow. The complaint charged that the hospital and one of its employees “failed to exercise the requisite degree of care and skill required.”

The hospital filed a motion to disqualify Bennett from representing Yerby. The motion was denied in the trial court and the denial was affirmed in the Court of Appeals. Crawford W. Long Memorial Hosp. of Emory University v. Yerby, 186 Ga. App. 407 (367 SE2d 245) (1988). We granted certiorari.

1. Both parties rely upon the long-standing rule that a lawyer is disqualified from representing a party against a former client in a matter that is “substantially related” to the lawyer’s prior representation. Tilley v. King, 190 Ga. 421 (9 SE2d 670) (1940). See also Summerlin v. Johnson, 176 Ga. App. 336 (335 SE2d 879) (1985).1

2. The circumstances of this case create a separate, though related, problem. Bennett has undertaken to represent a client who charged the hospital with negligent medical care. The conduct complained of occurred during the time that Bennett was providing continuing legal representation to the hospital in defending against several claims that charged the hospital with negligent medical care.

Lawyers in similar circumstances (i.e., an ongoing relationship with the hospital in defending medical-malpractice claims) of necessity would acquire a wide range of knowledge concerning the nature of medical care provided by the hospital. That would include knowledge (imparted to the lawyer by the client) of practices, policies, procedures, reporting requirements, and of ongoing or recurring problems — all as they pertained during this very period of time.

3. Bennett had acquired similar knowledge of (and from) his client as a result of representation that was ongoing at the time of Yerby’s death. That representation, of course, related to claims charging the hospital with negligent medical care. In this case, we need not determine whether the medical-malpractice claim that Bennett has brought against the hospital is “substantially related” to any of the eighteen medical-malpractice claims that he had defended on behalf *722of the hospital. The circumstance of representing a client against a former client in an action that is of the same general subject matter, and grows out of an event that occurred during the time of such representation, creates an impermissible appearance of impropriety. It is therefore prohibited by the Canons of Ethics.2 For this reason, the motion to disqualify should have been granted.

Judgment reversed.

concurring.

I concur in the judgment, and in doing so I emphasize that the opinion limits the mandate of disqualification to those cases in which the lawyer was actively representing the party in matters involving the same general subject when the events giving rise to the case in question occurred.

I am authorized to state that Justice Smith joins in this concurrence.