Harold Aryai Siegel, 68, an engineer-turned-lawyer who was the general counsel for Radiation Systems Inc. for more than three decades, died Sept. 13 at Washington Hospital Center of complications after open-heart surgery. He had lived in the Washington area since 1951 and in Greenbelt since 1963.

Mr. Siegel was born in Brooklyn, N.Y., and graduated in 1951 from the Massachusetts Institute of Technology with a degree in metallurgical engineering.

He decided to pursue law while working in Maryland at Engineering and Research Corp. There, he switched jobs from program manager to contract manager, a change that emphasized law over engineering.

Mr. Siegel attended night classes at Georgetown University law school and graduated in 1963. His specialty became contract law, and at different times since the mid-1960s he had offices in Riverdale, Dulles and Greenbelt.

Since June, he was working solely out of the Greenbelt space.

His clients included several firms with an engineering or technical focus, and his main client was Radiation Systems Inc., an antenna and communications systems firm in Dulles.

He was general counsel at RSI for 33 years, even though the company was purchased and sold a few times during the 1990s.

Mr. Siegel provided pro bono legal work to local organizations, including the Lakeside Homeowners Association since the 1960s and the Greenbelt Arts Center, which he helped incorporate in the 1980s.

He was a member of the Federal Bar Association and the American Bar Association as well as the bar associations of Maryland and Prince George's County. He also belonged to the American Institute of Mining and Metallurgical Engineers.

Mr. Siegel, a stamp and art collector, also loved sailing and kept a rare 1960 sailboat in Rose Haven, Md. There, he was a member of the Herrington Harbour Sailing Association.

His marriage to Consuelo Merrit ended in divorce.

He is survived by his second wife, Valerie L., of Greenbelt; six children from his first marriage; two children he adopted during his second marriage; seven grandchildren; and his mother, Ruth Siegel of Bethesda.