Specialty Laboratories Inc. said on Monday that Chief Executive Douglas Harrington will step down on March 29. The move follows by just four days the departure of chairman Richard Belluzzo.

Dr. Harrington is leaving the Valencia company, which provides medical testing services, to pursue other scientific and business ventures and well as to spend more time with his family, the company said in a press release.

The company credited Harrington with turning it around after government inspectors found unlicensed personnel working in its lab in 2001 and fined it $600,000. The problems delayed the company’s long-planned move from Santa Monica, which was finally completed last month.

Shares of the New York Stock Exchange issue were down nearly 8 percent in mid-afternoon trading to $9.38 on heavy volume.

The company announced the departure of Belluzo, the former chief operating officer of Microsoft Corp., on Feb. 10, citing his expanded responsibilities as chief executive of Quantum Corp. as the cause.