Allergological, clinical and histological findings in 109 unselected patients, treated for nasal polyps during the period Feb. 1977 to Feb. 1978 are reported. The material was divided into three groups according to clinical findings: 1) Atopy Group; 18 patients with positive history and skin test; 2) ASA Intolerance Group; 25 patients with a definite history of acetylsalicylic acid intolerance; and 3) Intrinsic Disease Group; 66 patients in whom specific etiological factors were not found. On skin testing, positive reactions were obtained in 42 patients. In 23 of the patients, the skin test result agreed with the history. Secretion and tissue eosinophilia, noted in 97 and 102 patients, respectively, correlated in 88% of the patients, whereas correlation with blood eosinophilia was poor (30%). The mean IgE level was 140 in the serum and 731 in the polyp fluid, serum values above 150 occurring in 28 out of 105 patients and fluid values above 150 in 58 out of 84 patients. The predominant histological finding in the polyp biopsies was tissue eosinophilia, which was most abundant in the ASA intolerance group. Squamous metaplasia was seen in 30% but it was marked only in 5 cases. In 10 patients ASA intolerance was confirmed by oral provocation.