Oral oxybutynin for treating hyperhidrosis is effective and safe. Its side-effects are mild but frequent so we consider whether transdermal oxybutynin (considered to have a better side-effect profile) could be an alternative for treating hyperhidrosis. During 2015, a prospective study was conducted. Epidemiological variables, effectiveness (using the Hyperhidrosis Disease Severity Scale) and tolerance to transdermal oxybutynin were compiled concerning two different groups (patients previously treated or untreated with oral oxybutynin), at baseline, and at 3 and 12 months. Seven previously treated and six previously untreated patients were included. Five patients in the first group discontinued the treatment within 3 months. Of the two remaining patients, one reported ineffectiveness and the other obtained an excellent response but discontinued due to local irritation. Among the untreated patients, two showed no response and four experienced improvement (three with "partial response" and one with "excellent response"). All patients discontinued treatment within 12 months. No major adverse effects were observed. The absence of active metabolites after transdermal oxybutynin could result in less effectiveness than oral oxybutynin, although it is usually well tolerated. In conclusion, transdermal oxybutynin could have low effectiveness for the treatment of hyperhidrosis in patients following intolerance to oral oxybutynin but could provide good results in patients who have never tried systemic drugs., (© 2017 Japanese Dermatological Association.)