James Spragine Long, 56, chairman of the board of Miller & Long, Inc., and affiliates, died Wednesday at Johns Hopkins University Hospital following heart surgery.

With a bopyhood friends, John F. Miller III, he founded the firm in 1947. The company grew from a two-man operation to become one of the largest concrete construction firms in this area.

It also added six affiliated companies and offices throughout the Middle Atlantic states. It was a pioneer in the use of electric climbing and track-mounted tower cranes. The Ellis clamp for 3-by-4 shores was made at its specifications and is now widely used.

Mr. Long served as president of the companies until this past January, when he became chairman of the board. He remained active in the companies until he suffered a heart attack March 5.

Born in Wilson, N.C., Mr. Long came to this area in 1934, and graduated from Woodrow Wilson High School.

Before cofounding Miller & Long, he worked for his stepfather, Luther W. High, Founder of High's Dairy Stores, and for S.D. Moses Co., a concrete construction firm and predecersor of Moses-Ecco, Inc.

Mr. Long Served as a navigator with the Army Air Forces in the South Pacific in World War II.

In 1965-66, he was national president of the Associated Builders and Contractors, Inc. He was a member of its board of directors for six years, and was president of the Metropolitan Washington Chapter in 1962, and a founder and first president of the ABC of Maryland in 1967.

Under Mr. Long's leadership, the ABC of sponsored the "Careers in Construction" film, produced by Stanford University in 1968.

He was on the board of directors of the American Society of Concrete Constructor for five years and was its membership chairman in 1968.

Mr. Long also was on the board of directors of the Capital City federal Savings and Loan Association of Washington.

He was a member of the Lay Advisory Council of Wesley Theological Seminary in Washington, and served on the administrative board of Bethesda United Methodist Church.

He belonged to the Columbia and Bethesda country clubs.

He is survived by his wife, Jane Lewis Long, and two sons, James Jr. and Edwin, of the home in Bethesda; three daughters, Mary Jane Euler, of Bethesda; Patricia A. Danoff, of Adelphi, and Nancy E. Beck of Damascus; his mother, Carrie Long High; a brother, Joe E. Long, and a sister, Edith L. Gamble, all of Bethesda, and three grandchildren.