This paper deals with the calculation of shadow wages for family labour in agriculture. Using the existence of a duality between input distance and cost functions, we use the former to derive individual labour shadow prices for a sample of Spanish citrus fruit producers. Our results show that the average shadow price representing the opportunity cost of family labour employed onfarm, is lower than the average market wage rate paid for hired labour. We relate this finding to a strategy of outsourcing of many growing tasks that is currently pursued by farmers to overcome the problems posed by a suboptimal farm size.