This is a review of factors affecting cross-sucking in group housed calves. Evidence is presented to indicate that cross-sucking is a re-direction of normal sucking behaviour. It is primarily seen when calves are fed milk or milk replacer rather than being allowed to suckle their mother. Prolonging the milk meal by reducing the flow rate (orifice size) in teat buckets reduces the problem of cross-sucking, as does leaving the buckets in the pen after the meal is ended. In large groups of calves, fed via computerized milk feeders, a protective stall for the calf that is drinking is helpful to reduce cross-sucking directed toward the drinking calf. However, both means of reducing cross-sucking in such conditions, reducing flow rate and protecting the drinking calf, reduce the number of calves that can be fed from a feeding station. Additional work is needed on determining the appropriate number of calves that can be fed from a computer controlled station while keeping cross-sucking within an acceptable level.