The discovery of a family with three members showing weak C^w antigen is described. In the proposita and her mother the ‘depression’ of C^w was very marked, while a half brother on the maternal side showed a strength of the antigen intermediate between that of the two and a normal C^w. In addition, a reduced strength of the e antigen was found in all three members, also in the two who had a presumably normal e gene on the other chromosome.