PURPOSE:Descriptive studies have indicated a rising trend in Hodgkin's lymphoma (HL) incidence in young adults, especially females. Increasing evidence has suggested that some risk factors associated with HL may vary by age or gender. Recent studies have reported an increased risk of HL associated with increasing body mass index (BMI), but the results have been inconsistent. The objectives of this study were to examine whether the associations between measures of body size (height, weight, and BMI) and HL risk vary by age and/or gender. METHODS:A population-based case-control study was conducted in Connecticut and Massachusetts. A total of 567 HL cases and 679 controls were recruited in 1997-2000. Unconditional logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (CIs). RESULTS:Among younger women <35 years old, being overweight (25-29.9 kg/m(2)) versus normal weight (18.5-24.9 kg/m(2)) was significantly associated with an increased risk of HL (OR = 2.1, 95 % CI = 1.1-4.0). The risk increased with increasing weight and BMI (p trends <0.01). Among women ≥35 years old, by contrast, higher weight and BMI were associated with a reduced risk of HL (p trends <0.01). Conversely, there was no significant association between BMI and risk of HL in younger or older males. CONCLUSIONS:These findings show that the associations between body size and risk of HL vary by gender and age, and require confirmation in other populations.