In the UK, under present Whitley Council Regulations for payment for out-of-hours pathology services, there is a complex relationship between the number of requests received, the time taken to analyse each request, and the number of calls for which payment may be claimed for work done. At a fixed average analysis time, the rate of increase of remuneration slows down as workload increases until at higher workloads remuneration falls. The introduction of methods with a shorter average analysis time to improve the clinical service increases remuneration disproportionately. We suggest that a fixed sessional payment would be a better way of funding the service.