Oocysts of Cryptosporidium species were identified in the faeces of scouring calves from a dairy farm. The faeces were watery and greenish yellow but the calves were usually alert and not desiccated when they were admitted to the clinic. Without treatment they became severely desiccated and recumbent within a few hours, but after symptomatic treatment they improved rapidly. The importance of cryptosporidiosis as a herd health problem is discussed.