The participation rate in medical screening programmes is typically below 100%, which means that not all potential health benefits are fully exploited. In this paper, the prospect of pecuniary compensation is tested as a method of increasing the participation rate. We propose a model explaining the individual's probability of participating ill screening for colorectal cancer when he is offered pecuniary compensation, given that lie did not participate when first invited. The participant's decision is based oil both known and uncertain factors. The estimation is conducted in two steps, where a binary probit model is used in each. We find that pecuniary compensation increases the probability of participation, and that an individual's participation probability systematically varies with variables such as travel expenses, income, age, education level, expected benefit from the screening, use of health-care services, genetic predisposition and subjective health status. Using the results from the estimation, we predict changes in the participation rate For different levels of compensation and estimate the cost per additional individual screened. The cost per additional individual screened is 808, including 25 in compensation; this cost increases with the level of compensation. Copyright (C) 2008 John Wiley & Sons, Ltd.