Twenty-six probands suffering from hidradenitis suppurative were identified from Hospital Activity Analysis (H.A.A.) records for the period 1980–83 and by direct referral from hospital specialists over a 6-month period in 1983–84. Investigation of their families eventually confirmed a total of 62 affected individuals from 23 families. In II families there was evidence in favour of single gene or Mendelian inheritance; in another three there was familial occurrence; in nine families there was a negative family history at the time of enquiry. The disease appears to be commoner than reports suggest and it is probable that there is an underestimation of affected individuals in our community. Problems of identification including variable age of onset and psycho-social factors were found and may be responsible for false-negative family histories.