The period of prevalence, 1988 inclusive, of Allergic Bronchopulmonary Aspergillosis (ABPA) and Allergic Bronchopulmonary Candiasis (ABPC), the two most frequently reported forms of allergic Bronchopulmonary Mycosis (ABPM), was investigated in an Irish regional hospital respiratory medicine outpatients, catchment area population 536,000. ABPM was defined by the presence of a majority of seven criteria: asthma, eosinophilia, elevated IgE, antibodies to Aspergillus Fumigatus or Candida Albicans, immediate skin test reaction to either fungus, culture of either fungus in sputum, and otherwise unexplained transient or permanent lung field x-ray abnormalities. New referrals were investigated for ABPM if they had asthma and eosinophilia, or asthma and lung field x-ray abnormalities. Fourteen patients with ABPM were identified from a total of 1390 new referrals, a period prevalence of just over one per cent. It is concluded that (1) ABPM is a relatively common disorder in an Irish regional hospital respiratory medicine outpatient population and (2) ABPC constitutes a higher proportion of this disorder than previously considered.