A field trial was conducted to compare the efficacy suspensions of betamethasone alcohol with dexamethasone trimethyl acetate on the induction of parturition before term in dairy cows. Initial treatment consisted of a subcutaneous injection of either 20 mg of betamethasone as a 10 mg/ml suspension(Group A), 30 mg of a 15 mg/ml suspension(Group B), or 20 mg of dexamethasone TMA(Group C). Those cows not calving within 10 days received a further 25 mg of betamethasone alcohol as a 2 mg/ml suspension. Data were collected from 619 cows on 41 farms. A marked difference between groups was noted in the proportion of animals calving to the initial injection (55.0, 61.4 and 26.4% calved to first injection in Groups A, B and C respectively); the differences between the groups receiving the betamethasone suspensions and the group receiving dexamethasone trimethyl acetate were highly significant (P<0.001). Of the animals treated 6.9, 3.6 and 10.2% failed to calve within 17 days of the initial treatment in Groups A, B and C respectively (Group B significantly different from Group C (0.02 > P> 0.01). Nevertheless, the response-time (mean of 7.5 days for all those calving to the first injection, and of 12.4 days for all those calving to the second injection) was not significantly different between the three treatment groups. Calf mortality over all treatments was 15.2% at birth and 26.6% by 4 days old. The incidence of metabolic disease was 5.9%, and 203% of cows had retained foetal membranes 24 hours after calving. No differences were observed between groups in the incidence of dystocia and cow mortality. Four cases of mastitis were recorded in Group A and 12 cases in Group C. No cases were recorded in Group B.