The origins of occupational sex-types are investigated by studying the feminization of clerical work. Two British firms are contrasted, the General Post Office, which used female clerks, and the Great Western Railway, which used male clerks. The main finding is that offices and firms whose labor force was predominantly nonclerical tended to use male rather than female clerks. This is because the high proportion of nonclerical labor costs in these offices made it economical to budget relatively higher clerical labor costs, thus permitting more expensive male labor.