For the last century the industrialized capitalist nations have been characterized by a tendency to reduce the length of time employees spend at their place of paid employment. Within the contemporary economic and industrial relations literature, there are two primary contending explanations for this phenomenon. The neoclassical tradition argues that the change in standard times is primarily a consequence of rising wages, while Marxists claim that it is principally a manifestation of rising work intensity. The essence of these two hypotheses is outlined in this paper and the contemporary empirical evidence underpinning each is surveyed. It is concluded that, at this stage, the Marxist thesis would appear to have greater theoretical and empirical substance than that offered by the defenders of the rising income hypothesis.