Aspartame (Nutrasweet ®, APM) is a widely used artificial sweetener synthesised from aspartate and phenylalanine, both of which are freely available in the normal diet but known to exert toxic and teratogenic effects when consumed in large quantities. While APM's protagonists claim that it is the most thoroughly researched food additive ever, there have been only a handfull of studies on it's behavioural effects. This study examined the behavioural teratogenic effects of APM in the offspring of rats which were exposed throughout pregnancy to solutions containing 0.05% or 0.10% APM or a buffered control solution. The animals were tested in the Hughes exploration box and the 12-arm radial maze using six arms baited at the beginning of each trial and lowering guillotine doors each time the rat returned to the centre of the maze to prevent the rats from adopting response strategies. In the Hughes exploration box, control and APM animals showed a preference for novelty. There were no difference between groups on measures of exploration and ambulation. In learning the radial arm maze task, there were no differences in the number of errors made by the groups and all animals learned the task to a high degree of proficiency. However, during the first half of the 40 sessions and relative to controls, the rats prenatally exposed to the 0.10% APM solution took significantly less mean time to enter the arms of the maze for the first six arm entries; the time taken by the 0.05% APM group generally fell between that of the control and 0.10% APM group. These results suggest that APM may have a dose-dependent effect on the time taken by rats to enter an arm in the radial arm maze. The validity of these results is limited by some methodological considerations, such as the relatively low genetic diversity of the groups, and this study is in need of replication. Despite these caveats, this study is significant as it is the only behavioural teratology study with APM to use an adequate cross-fostering procedure, a low dose of APM and report a dose-dependent behavioural effect. The discussion offers suggestions for future research that could improve our knowledge of the possible behavioural teratogenidty of APM.