A plant breeding program, extending over several years, accumulates records of the progeny obtained from numerous crosses, made according to no systematic plan. This paper describes the fitting of additive parental main effects, or 'combining abilities,' to such data. It examines the feasibility and practical utility of the analysis, using data on English apples (from this Institute) and on rubber (supplied by the Rubber Institute of Malaya). The analysis is a straight forward application of least-squares, involving no new statistical theory.