An outbreak of Corynebacterium pseudotuberculosis infection in an Israeli dairy herd appeared in four clinical forms: cutaneous, mastitic, visceral and a mixed form. Only cows were affected and susceptibility increased with age. Most cases occurred during a short period in the summer months. The total morbidity rate was 13.7 per cent involving 41 cows. Thirty cows were affected by the cutaneous form, five by the mastitic form, four by the mastitic and cutaneous forms, one by the mastitic and visceral forms and one by the visceral form. The cutaneous form appeared as one or two pyogranulomatous lesions affecting the body or head. Subclinical to severe clinical mastitis was found in the mastitic form. In the visceral form the upper and lower respiratory system were affected by multiple purulent lymphadenitis. All the cutaneous lesions recovered irrespective of treatment. Mastitis did not respond to treatment and severely affected milk production in most cases. All the isolates of C pseudotuberculosis were nitrate reductase negative. Most isolates were sensitive to norfloxacin, cephalothin, methicillin, kanamycin and furazolidone and resistant to ampicillin, lincomycin and neomycin.