The present study investigates the factors explaining the number of hours invested in new ventures of female and male entrepreneurs. For new ventures in particular time investment is an important issue, in particular as series of (usually) new and non-recurrent activities is undertaken, laying the foundation of the firm and securing its viability. A distinction is made between factors that influence the number of working hours through preferences or productivity. To test for influences on allocation and the productivity of work time a nonlinear model is proposed that is tested using data of 1256 Dutch business owners (919 male and 337 female) who started a business in 1994. Findings indicate that time invested in the business is determined by various aspects of human, financial and social capital, availability of other income, outsourcing activities and gender. It is shown that some of the identified factors relate to preferences and others to productivity. Women appear to invest less time in the business than men, which is due to an on average lower productivity of work time. This lower productivity can - in turn - be attributed to lower amounts of human, socialm and financial capital of female entrepreneurs, as well as specific ambitions or goals, not directly related to economic performance.