The aim of this study was to assess the preventive action of Pycnogenol® (Horphag Research Ltd, UK) on cramps and muscular pain in different groups of subjects and patients. The study included a 5-week observation period (4 weeks treatment and one follow-up week after the suspension of treatment) to evaluate the efficacy of Pycnogenol after its withdrawal. Four 50 mg capsules (total dose 200 mg/day) were prescribed with suggestion to drink at least 1.5 liters of water every day. In the first part of the study 66 healthy subjects completed a 5-week follow-up period. The difference between number of cramps attacks recorded within the 2 weeks before inclusion and the number of episodes during the fourth (p <0.05) and fifth (p <0.05) week were statistically significant. In normal subjects the average number of episodes was reduced from 4.8 (1.2) events per week to 1.3 (1.1) at 4 weeks (p <0.05). In venous patients the decrease in events was from 6.3 (1.1) to 2.6 (0.4) per week (p <0.05). In athletes the number of episodes decreased from 8.6 (2) to 2.4 (0.5) (p <0.05). The decrease was still present at 5 weeks in the 3 groups, to levels significantly lower than inclusion values (p <0.05). In the second part of the study, patients with intermittent claudication and diabetic microangiopathy were evaluated and treated (4 weeks). The groups treated with Pycnogenol and the control, placebo groups were comparable. There was a significant decrease in the number of cramps episodes (p <0.05) and in the score concerning muscular pain (p <0.05) in claudicants and diabetics. No significant effects were observed in the placebo groups. In conclusion, cramps and muscular pain, common in these 2 types of patients, were decreased by the use of Pycnogenol. Globally, these results suggest that the use of Pycnogenol prevents cramps, muscular pain at rest, and pain after/during exercise in normals, in athletes prone to cramps, in patients with venous disease, in claudicants, and in diabetics with microangiopathy. The difference is statistically significant considering objective observations (cramps episodes) and evaluating more subjective aspects (score). This indicates that Pycnogenol is effective in reducing pain and cramps during retraining and rehabilitation increasing its efficiency. In starting any physical rehabilitation program, particularly in vascular subjects, the limitation in mobility associated with muscular pain and with cramps tends to be relevant, and controlling these symptoms is useful to speed up the retraining process.