Topical minoxidil, used in the treatment of baldness, has been commercially available since 1987. Its systemic side effects are rare. We observed an as yet unreported "polymyalgia syndrome" in four otherwise healthy males whose sole medication was topically applied minoxidil. They experienced fatigue, weight loss and severe pain in the shoulders and pelvic girdle, suggesting connective tissue disease. Three patients had a transient rise in liver enzymes, while other laboratory analyses remained normal. Tritanomaly was detected in two patients who underwent systematic color vision testing. All symptoms disappeared after withdrawal of minoxidil. Rechallenge was positive once in one patient and twice in another. The mechanism of this side effect remains to be determined.