Abstract PURPOSE: Fetal and early life events have been associated with diseases that develop later in life. Low birth weight and the adult onset of hypertension, coronary heart disease, cerebrovascular disease, and non-insulin dependent diabetes have been identified. As well, associations with breast, ovarian, and prostate cancer to high birth weight have been found. An assessment of birth weight and cancer incidence was conducted in a cohort of black and white residents under the age of 46 years. METHODS: Cases were obtained from the Savannah River Region Health Information System cancer registry incident cases (1991–1995) and were limited to South Carolinians born in 1950 and later. Controls were obtained from birth certificate records by choosing the next two records after a cancer case record that matched on year of birth, race, and sex. Results were obtained for 117 cancer cases and 238 controls. RESULTS: After examining the birth distribution, the births were split into two groups based on mean birth weight among controls (3215 grams). Conditional logistic regression (CLR) showed that individuals with higher birth weights (> = 3215 g) were 1.65 (95% CI = 1.03–2.64) times more likely to be cancer cases than those with lower birth weights. When weights were categorized into 500 g increments, a CLR Score statistic showed there was a significant trend (p = 0.0006) of increasing proportion of cancer cases with increasing birth weight. Eight out of the eight cases of lymphoma had birth weights greater than 3579 g. CONCLUSIONS: The results of this preliminary study suggest that cancer incidence among the young may be associated with higher birth weights. One possible reason for this finding, which requires further investigation, might be that larger infants are exposed to higher levels of hormones and/or growth factor than smaller infants in utero that might increase the risk of certain cancers later in life. This may be suggestive of possible environmental factors affecting early growth. These findings support the need for additional study of this association.