To understand better the clinical impact of periodic limb movements during sleep (PLMS) we analysed data from 51 patients who, following an adaptation night, presented a PLMS index > 5 during two consecutive nocturnal polysomnographic recordings. In the morning following each recording patients completed a questionnaire including five visual analogic scales (VAS): (1) I did not sleep well/I slept very well. (2) I feel very sleepy/I do not feel sleepy at all. (3) I feel very tired/I feel very dynamic. (4) Physically, I do not feel fit/physically, I feel fit. (5) Psychologically, I do not feel fit/psychologically, I feel fit. We compared the responses to these questions with the PLMS index, first inter-individually, then intra-individually between nights. RESULTS: The inter-individual analysis did not show correlations between the PLMS index and the questions (1) and (2). We found a significant correlation between the PLMS index and the questions (3) (r = -0.29; P < 0.05), (4) (r = -0.30; P < 0.05) and (5) (r = -0.39; P < 0.01). For the intra-individual analysis, we did not find correlations between the PLMS index and questions (1)-(3), but found a significant correlation with questions (4) (r = -0.28; P < 0.05) and (5) (r = -0.36; P < 0.01). CONCLUSION: PLMS per se, or the sleep changes induced by them, seem to be associated with decreased physical and psychological fitness on awakening.