Using data from a case-control study in the United States (the Selected Cancers Study), we examined the relationship between non-Hodgkin's lymphoma (NHL) and family history of different cancers. Cases were 1,511 men aged 31 to 59 years and diagnosed pathologically with non-Hodgkin's lymphoma during 1984-88. Controls were men, frequency-matched to cases by age range and cancer registry (n = 1,910). All study subjects with acquired immunodeficiency syndrome were excluded from analyses. Our results showed that the risk of NHL is associated with a history of lymphoma (odds ratio [OR] = 3.0, 95 percent confidence interval [CI] = 1.7-5.2) and hematologic cancer (OR = 2.0, CI = 1.2-3.4) in first-degree relatives after adjustment for age, ethnic background, and educational level. Further analyses were performed for the subgroups defined by age at diagnosis (younger than 45 years cf 45 years or older). The association of NHL with a family history of lymphoma and hematologic cancer was found primarily among men aged 45 and older (OR = 4.1, CI = 1.9-8.8 for lymphoma and OR = 2.3, CI = 1.3-4.0 for hematologic cancer). The association among men aged 45 and older did not vary by whether or not there were any familial patients diagnosed at the age of 45 or older. No significant associations could be found for a family history of lung cancer, breast cancer, prostate cancer, colon cancer, skin cancer, liver cancer, stomach cancer, brain cancer, thyroid cancer, or myeloma. This study suggests that the familial risk of NHL is influenced primarily by hematolymphoproliferative malignancies rather than other cancers. The familial effects of hematolymphoproliferative malignancies may be stronger for men aged 45 to 59, compared with those aged 31 to 44.