Occupational skin diseases are very common among hairdressers. The aim of our study was to evaluate the frequency, the age distribution and the source of contact sensitization in a group of 209 hairdressers who consulted our Clinic from 1990 to 1999. One hundred and thirty-two patients showed one or more clinically relevant positive reactions to different allergens; 89 of them were positive to the hairdressers' series and 43 were positive to other allergens. Para-phenylenediamine base and para-toluenediamine sulphate caused the greatest number of positive reactions (77 and 29 respectively). Both glyceryl monothioglycolate and ammonium persulphate gave 25 positive patch tests. The allergens not included in the hairdressers' series which gave the greatest number of positive reactions were nickel sulphate and disperse dyes yellow 3, blue 124 and red 1. The allergens known as strong skin sensitizers have remained almost the same over the years. Preventive measures should be mandatory to protect hands and to improve the safety of this job.