Residents of at least three Harvard Houses have received a series of obscene phone calls in the early morning hours during the past week.

James A. Sharaf '59, attorney in the Office of General Counsel, said that students in Adams, Currier, North Houses and two graduate dorms, Ames and Wyeth Halls, have received "a pattern of calls that tend to blanket an entire building in the small hours of the morning between midnight and 5 a.m."

Adams House has been the most frequent target, Sharaf said. Residents said that calls were received for four consecutive nights last week.

Efforts are being made to stop the calls, Sharaf said. "With the consent of students involved, we have installed some systems to deal with the problem," he explained. He declined to specify the nature of the devices.

He also urged students to hang up once the nature of the call is evident. "Even listening to these people, much less talking to them encourages this behavior," Sharaf said.

The caller will only speak to women, according to students in Adams. He hangs up if a male voice answers, Sharaf said.

One Adams House resident said that the most upsetting aspect of the calls is their late hour. One target of the caller said the late hour was more upsetting than the obscene content.

Sharaf said that more than five dorms may be receiving obscene calls. Often people do not report the calls unless they are aware others are also getting them.

James T. O'Shea, telecommunications manager of Buildings and Grounds, said his department is working with the telephone company on the problem.