Ronald C. Vermillion, 49, a reinforced iron worker who was active in union affairs, died Tuesday of a cerebral hemorrhage while in the office of a Washington lawyer on business matters.

A member of Local 201 of the Intenational Association of Bridge, Structural Steel and Ornamental Iron Workers for 25 years, he had served as a business agent of the union local from 1965 to 1975.

Mr. Vermillion was born in Martinsburg, W. Va. He served with the Navy in World War II, seeing combat duty in the Pacific aboard destroyers and destroyer tenders.

He came to this area after the war and worked as general foreman for major construction companies on such projects as the RFK Stadium and more recently on Metro.

Mr. Vermillion was a member of the Veterans of Foreign Wars unit in Morningside and of Camp Springs Lodge No. 227 of the Masons.

He is survived by his wife, Loretta, and two daughters, Katherine and Kimberly, all of the home in Camp Springs; two brothers Tommy and Charles Lee, and two sisters, Tanya Porter and Lelia Holley, all of Clearwater, S.C., and three other sisters, Juanita Moore, of Monroe, N.C., Phyllis Hamlet, of North Augusta, S.C., and Danese Lillie, of Southgate, Mich.