Cytoplasmic male sterility in sugar beet was successfully transmitted across the union where male sterile and equivalent O-type plants were reciprocally grafted. Two experiments are described. In the first, 30 pairs of developing flowering stems were exchange-grafted between male-sterile and O-type plants. Fifteen O-type scions exhibited full or partial male sterility when grafted to male-sterile stocks and sterility was observed in progeny from these in eleven cases. In flowers from side shoots of O-types grafted with male-sterile scions eight cases exhibited some male sterility and progeny from four of these retained the sterility. In the second experiment O-type seedlings were grafted to male-sterile seedlings and out of the 22 success-fully raised to flowering, male sterility was exhibited in 12 of them. Male sterility occurred among progeny of all 22, even where the sterility could not be detected in the scions. In six cases where the scion appeared fully male-sterile no pollen was produced in any of the progeny.