To measure direct response to single trait selection for milk yield and correlated response in health problems, two homologous base populations were formed by pairing 66 Holstein females by sire. Base populations and descendants were managed identically except for selection by milk yield. One base and lineage were mated with sires with highest predicted difference milk (selection group); other base and lineage were mated with average sires in 1964 (control group). Milk yield, supplemental labor, and veterinary and semen expense were recorded specific to each cow. Over 9 yr, 130 selection and 163 control cows were observed. Selection cows yielded more milk but with increase in labor and expense for health care. Estimates of labor for the selection group were greater for mammary, locomotion, and digestion categories and for expense in mammary, respiration, first insemination, and later insemination categories. Labor and expense for reproduction did not differ for genetic groups. Differences between groups in annual estimated labor and expense totaled $27.00. Extra income over feed cost more than compensated for greater health care and semen cost; however, the magnitude of the latter indicates a need for them to be considered when economically evaluating breeding programs where major emphasis is on milk yield.