Why do Canadian mothers have lower incomes than women who have never had children? Microdata from the 1995 GSS allow examination of two hypotheses: 1. mothers have spent more time out of the labour force, thus acquiring less human capital; 2. higher levels of unpaid work lead to fatigue and0or scheduling difficulties. Measuring work history does little to account for the ‘family gap. ‘The estimated child penalty is reduced by allowing for ‘human capital depreciation’ and controlling for unpaid work hours, but the two hypotheses together cannot entirely explain the gap.