Fairfax County Circuit Court Judge Richard J. Jamborsky, known to his colleagues for a kind and gentle manner on the bench and off, was selected by them yesterday to be the court's next chief judge, succeeding Lewis H. Griffith, who will step down June 30.

Jamborsky, 53, who has been a judge since 1968, will take control of the busiest and largest circuit court in Virginia, a court that is expected to hear 20,000 cases in the next year. Jamborsky will assign cases to his fellow judges and serve as chief administrator of the court's judicial business.

Griffith, 59, announced two weeks ago to the surprise of many in the court and legal community that he will relinquish his post as chief judge, which he has held about 2 1/2 years. Griffith, who said he wanted more time for personal and professional activities, will continue to serve as a substitute judge after Oct. 1.

Jamborsky said yesterday that he hoped to follow suit in the steps of Griffith, who has been praised for initiating dramatic changes in the court, including making the court more accessible to the public and creating programs to help speed the docket.

"Whoever thought Judge Griffith was going to leave when he did?" Jamborsky said. "Last month Judge Griffith was chief judge and we were sailing along."

Yesterday, during a regular monthly meeting, the 13 judges voted after discussing the direction of the court. Jamborsky was selected unanimously, Griffith said.

Jamborsky said the demands of his new job will force him to get up earlier to do his daily running. He plans on running his 20th Boston Marathon next spring.

Jamborsky grew up in Savannah, Ga., in a row house with his grandmother. He said his fascination with law goes back to the time when he lived in Tennessee and heard stories about Tennessee lawyer John R. Neal, who was a defense attorney in the famous Scopes evolution trial.

Jamborsky, who graduated from George Washington University law school in 1963, was the county's first legal aid attorney. He became a judge in 1968 when he was appointed to the Fairfax County Juvenile and Domestic Relations District Court. He became chief of that court in 1975. He was then appointed to the county's Circuit Court in 1976.

Jamborsky, who lives in Reston and is separated from his wife, has three grown sons.

"We're very proud of Judge Jamborsky for his service on the bench as well as his extracurricular activities," Griffith said. "I think Judge Jamborsky has the abilities, the integrity, the legal scholarship . . . to make a great chief judge."