The relationship between socio-economic characteristics, previous tonsillectomy, family history of cancer and risk of Hodgkin's disease (HD) was investigated in a case-control study. One hundred and sixty patients, aged 15-78, with histologically confirmed HD, and 185 hospital controls were interviewed. A statistically significant decrease in risk of HD was observed among subjects with large sibship size (RR = 0.63, C.I. 0.46-0.86) and among those who underwent tonsillectomy prior to the age of 10 (RR = 0.46, C.I. 0.22-0.94). High educational level was associated with an increased risk of HD (RR = 6.68, C.I. I.94-23.08). Analysis by age-group (15-39 yrs and 40 yrs or more) confirmed the role of high educational level as a risk factor in both young and old subjects, while the protective effect of tonsillectomy at an early age seems to be confined to young subjects. Analysis by histological subtype showed a statistically significant decrease in risk of HD in large sibship size for both nodular sclerosis (NS) and mixed-cell subtypes; the role of education and tonsillectomy was observed only for NS. These data confirm the role of social factors in HD risk and suggest a protective effect of tonsillectomy performed early in life that needs to be confirmed in larger population-based studies.