The number of infiltrating eosinophils were counted in tumour specimens from an unselected material of 140 cases of primary Hodgkin's disease (HD) and divided in three groups. Twenty-six cases (19 per cent) showed heavy infiltration (> 200 eosinophils/10 vision fields (VF)), 51 (36 per cent) moderate infiltration (11-200 eosinophils/10 VF and 63 virtually no infiltration (< 10 eosinophils/10 VF). The eosinophilic infiltration was significantly more pronounced in the nodular sclerosis subtype. Cases with heavy infiltration had a significantly worse disease-free survival compared to other cases. In a multivariate analysis, heavy eosinophilic infiltration was the most important factor for determining disease-free survival in all patients and also when patients above and below 60 were analysed separately.