An exploration of the vital role played by Mexican seasonal workers in Canadian agriculture and how they have become a structural necessity in some sectors. Based on interviews with Leamington greenhouse growers and migrant Mexican workers, Tanya Basok offers a timely analysis of why the Seasonal Agricultural Workers Program is needed. She argues that while Mexican workers do not necessarily constitute cheap labour for Canadian growers, they are vital for the survival of some agricultural sectors because they are always available for work, even on holidays and weekends, or when exhausted, sick, or injured. Basok exposes the mechanisms that make Mexican seasonal workers unfree and shows that the workers' virtual inability to refuse the employer's demand for their labour is related not only to economic need but to the rigid control exercised by the Mexican Ministry of Labour and Social Planning and Canadian growers over workers' participation in the Canadian guest worker program, as well as the paternalistic relationship between the Mexican harvesters and their Canadian employers.