We used the nationwide Swedish Family-Cancer Database to analyze the risk for soft tissue tumors in offspring by parental cancers and in siblings of soft tissue tumor probands. Additionally, risk for second cancer following soft tissue tumor was investigated. In offspring, 1488 soft tissue tumors were diagnosed between years 1958 and 1996. Groups of offspring were compared by calculating standardized incidence ratios (SIRs) for soft tissue tumors. Parental breast, prostate and connective tissue cancers were associated with offspring soft tissue tumors in sex- and age-specific groups. The SIRs were of borderline significance, suggesting a small etiological contribution by Li-Fraumeni syndrome. Soft tissue tumors conveyed a high risk of second soft tissue tumor, probably partially due to recurrences. However, the observed risk for second nervous system cancer was consistent with Li-Fraumeni syndrome. Other associations were unlikely to be due to Li-Fraumeni or other known syndromes, but they could be spurious findings arising from multiple comparisons. Among these, parental stomach cancer (SIR 3.19, 95% CI 1.69-5.17) and endocrine gland tumors (SIR 3.66, 95% CI 1.32-7.17), particularly parathyroid tumors (SIR 4.46, 95% CI 1.41-9.23), were associated with offspring fibrosarcoma, and parental breast cancers with offspring leiomyosarcoma (SIR 2.04, 95% CI 1.08-3.30).