OBJECTIVES The influence of body size on dialysis-related mortality among Asians and Pacific Islanders--heterogeneous ethnic groups with dissimilar body compositions--is poorly understood. Our study objective was to compare the relations of body size and mortality among patients with end-stage renal disease of different ethnicities. DESIGN, SETTING, AND PARTICIPANTS We examined data from a cohort of 21,492 adult Asians, Pacific Islanders and non-Hispanic Whites who initiated dialysis during 1995-2003 within California, Hawaii and the US Pacific Islands. MAIN OUTCOME MEASURE Time to death through September 22, 2008. RESULTS Among both men and women, Pacific Islanders were the heaviest and Whites the tallest of the ethnic groups examined. Annual mortality rates were highest among Whites (29.6%), intermediate among Pacific Islanders (18.8%) and lowest among Asians (17.3%). Larger body size was associated with lower mortality among Pacific Islanders, Whites and most Asians on dialysis after adjustment for patient-level sociodemographic and clinical factors, area-based socioeconomic status and geographic clustering. Filipinos were the exception to this rule and showed a trend towards higher mortality with increasing body size. These findings were consistent irrespective of how body size was measured. CONCLUSIONS Larger body size is associated with lower mortality among Pacific Islanders, Whites and most Asians on dialysis. Use of disaggregated ethnicity data may enhance our understanding of how ethnicity- or community-specific factors influence body size, body composition and dialysis-related outcomes in these diverse populations.