The incidence of non-Hodgkin's lymphoma (NHL) has been increasing rapidly over the last three decades. The reasons for this trend are not known although increasing exposure to sunlight has been postulated. We used data from the New South Wales Central Cancer Registry to analyse second primary neoplasms following NHL diagnosed between 1972 and 1995, to identify possible common causal agents. A total of 12,452 patients contributed 54,308 person-years of follow-up during which time there were 705 second primary neoplasms compared to 592.99 expected (standardized incidence ratio (SIR = 1.19, 95% confidence interval (CI) 1.10-1.28). There were excesses of melanomas of skin (SIR = 2.38, 95% CI 1.92-2.91), lip cancer (SIR = 2.74, 95% CI 1.59-4.38), tongue cancer (SIR = 2.53, 95% CI 1.09-4.99) and bladder cancer (SIR = 1.64, 95% CI 1.19-2.21). There was also over a threefold excess in soft tissue sarcomas (SIR = 3.61, 95% CI 1.80-6.45) and in thyroid cancer (SIR = 3.42, 95% CI 1.56-6.49). The SIR for myeloid leukaemia was 0.78 (95% CI 0.28-1.69). The increases in melanoma of the skin and cancer of the lip and tongue among patients with NHL strongly suggest sunlight exposure as a shared causal agent. The increase in soft tissue sarcomas might be due to shared effects of exposure to chemicals such as phenoxy acid herbicides. The increases in bladder and thyroid cancers are likely to be explained by effects of treatment for NHL. We did not find a chemotherapy related increased risk of myeloid leukaemia among NHL patients.