CHICAGO  Ralph Medley, a retired professor of philosophy and English who is black, remembers the day he was arrested on his own property, a rental building here in Hyde Park where he was doing some repair work for tenants.

A concerned neighbor had called the police to report a suspicious character. And that was not the first time Mr. Medley said he had been wrongly apprehended. A call Mr. Medley placed to 911 several years ago about a burglary resulted with the police showing up to frisk him.

“But I’m the one who called you!” he said he remembers pleading with the officers.

Like countless other blacks around the country, Mr. Medley was revisiting his encounters with the police as a national discussion about race and law enforcement unfolded after the arrest of Henry Louis Gates Jr., Harvard’s prominent scholar of African-American history. Professor Gates was arrested for disorderly conduct July 16 at his home in Cambridge, Mass., as the police investigated a report of a possible break-in there. The charge was later dropped, and the Cambridge Police Department said the incident was “regrettable and unfortunate.”

In interviews here and in Atlanta, in Web postings and on television talk shows, blacks and others said that what happened to Professor Gates was a common, if unacknowledged, reality for many people of color. They also said that beyond race, the ego of the police officer probably played a role.