The aim of this study was to determine whether there is a practice effect on the Hand Laterality Judgement Task (HLJT). The HLJT task is a mental rotation task that can be used to assess motor imagery ability in stroke patients. Thirty-three healthy individuals performed the HLJT and two control tasks twice at a 3-week interval. Differences in the accuracy and the response times were analysed. The results for all three tasks showed a decrease in the response time between the first and the second assessments (8-20%), and, for the HLJT, also a small (3%) but relevant increase in accuracy. The most likely factor explaining this improvement is that of practice effects. This implies that an improvement in the HLJT scores found over time in clinical research may be partly because of a learning effect, which has to be taken into account when interpreting the results. It is likely that a practice effect occurs in repeated measurements of the HLJT. (Contains 1 table.)