The health impacts of exposure to summertime heat are a significant problem in New York City (NYC) and for many cities and are expected to increase with a warming climate. Most studies on heat-related mortality have examined risk factors at the municipal or regional scale and may have missed the intraurban variation of vulnerability that might inform prevention strategies. We evaluated whether placebased characteristics (socioeconomic/demographic and health factors, as well as the built and biophysical environment) may be associated with greater risk of heat-related mortality for seniors during heat events in NYC. As a measure of relative vulnerability to heat, we used the natural cause mortality rate ratio among those aged 65 and over (MRR65+), comparing extremely hot clays (maximum heat index 100 degrees F+) to all warm season days, across 1997-2006 for NYC's 59 Community Districts and 42 United Hospital Fund neighborhoods. Significant positive associations were found between the MRR65+ and neighborhood level characteristics: poverty, poor housing conditions, lower rates of access to air-conditioning, impervious land cover, surface temperatures aggregated to the area level, and seniors' hypertension. Percent Black/African American and household poverty were strong negative predictors of seniors' air conditioning access in multivariate regression analysis. (c) 2014 The Authors. Published by Elsevier Ltd.