This paper analyses changes in the employment rates and hours worked of mothers with pre-school age children in Australia between 2002 and 2008, using data from Waves 2 to 8 of the Household Income and Labour Dynamics in Australia survey, a large-scale longitudinal survey of the household population. The employment rate of mothers with young children rose considerably over the period considered. However, the hours per employed mother changed relatively little on average. There are significant differentials in the mother's employment rate by the number and ages of children, and by mother's education, marital status and birthplace. Hours worked per employed mother vary with the mother's age, education, marital status and birthplace, by the youngest child's age, and the number of children under five. The paper pays particular attention to the change in these differentials over time. It finds the change over time for the mother's employment rate varies significantly by the number of children, while for the hours worked it varies by mother's education and marital dissolution, and the age of the youngest child. The implications of these patterns are discussed.