One hundred and eleven dairy cows with digital dermatitis, on six commercial farms, were used to test the efficacy of a footbath containing erythromycin for treating the condition. Four days after 55 of the cows had walked through the footbath after two successive milkings their lesions were significantly less active and painful than those of the 56 untreated cows. These 56 cows were then treated in the same way and both groups were re‐examined seven days later. There were no significant differences between the clinical signs observed in the two groups, and the benefits of the treatment had persisted for the 11 days of the trial.