1. A total of sixty, 7-day-old British Friesian male calves, reared on a conventional early-weaning system, were used in two experiments in which dried skim milk was partially replaced by levels of 7, 14 and 21 % cooked potato flour (CPF). In the first experiment the diets were iso-energetic but differed in total nitrogen contents, whilst in the second experiment, casein was used to make the diets iso-nitrogenous. 2. In both experiments, diets containing CPF depressed growth rate from 4 to 18 days on treatment (11 to 25 days of age) and reduced the firmness of the faeces. These effects were correlated with the concentrations of CPF in the diets, live-weight gain being depressed by 20%, and the firmness of the faeces by 14%, for each 10 % inclusion of CPF. After 18 days on treatment (25 days of age) these effects became less pronounced. 3. The overall performance of calves to weaning (after 35 days on treatment) was similar on all diets. Daily live-weight gains from 4 to 56 days and 35 to 56 days did not differ between treatments. 4. It was concluded that whilst the inclusion of CPF in the diets of milk-fed calves was unlikely to have any permanent effect on the live weight of calves at 5 or 8 weeks of age its use in milk diets for calves of less than 3 weeks of age must be limited if loose faeces are to be avoided.