Background: Though interdialytic weight gain (IDWG) is used as an index of fluid and dietary compliance among hemodialysis patients, neither its clinical correlates nor an actual ‘normal range’ is established. Consequently, clinicians impose uniform dietary and fluid restrictions to limit IDWG, hoping to avoid symptomatic intravascular volume overload. Methods: We studied 309 stable hemodialysis patients over a 3-month period to determine the spectrum of their IDWG and the relation between IDWG, dry weight, nutritional and demographic parameters. Results: Mean IDWG was 2.8 ± 1.2 kg (range –0.8 to 8.2 kg). Dry weight had a direct correlation with actual IDWG (r = 0.31; p = 0.001) but an inverse correlation with percent IDWG (r = –0.25; p = 0.001). IDWG was less in older patients (r = –0.34; p = 0.001) even after adjustment for dry weight. Actual IDWG was greater in men than women (3.1 ± 1.2 vs. 2.5 ± 1.2 kg, p = 0.001), but was equivalent after adjustment for dry weight (men 4.2 ± 1.8%; women 3.9 ± 1.9%, p = 0.1). Hematocrit (r = 0.14; p = 0.02) and serum creatinine concentration (r = 0.18; p = 0.02) had direct correlations with IDWG. Conclusions: We conclude that IDWG in hemodialysis patients is proportional to body weight. Differences in body weight explain excess IDWG in men but not in younger hemodialysis patients. Fluid and dietary restrictions in hemodialysis patients should be individually prescribed as opposed to a fixed amount irrespective of body weight.