Qualitative analysis of the literature on cognitive side-effects of lithium in patients with a bipolar disorder identified four of 17 studies that fulfilled criteria of adequate methodological quality. Analysis of these four studies showed that lithium had a negative effect on memory and speed of information processing, often without subjective complaints or awareness of mental slowness. The consequences of these findings for daily practice are discussed, in particular with respect to driving performance. When neurocognitive complaints or deficits are present, lithium plasma level, thyroid functions and degree of mood disturbance should be assessed. In cases where all these parameters are within normal limits and neurocognitive complaints still persist, dose reduction of lithium, thyroid hormone addition, prescription of a slow release preparation or replacement of lithium by another moodstabiliser should be considered. Guidelines are suggested with respect to further neuropsychological screening.