Consideration of the relationship between residential floor level and concentration of traffic-related airborne pollutants may predict individual residential exposure among inner city dwellers more accurately. Our objective was to characterize the vertical gradient of residential levels of polycyclic aromatic hydrocarbons (PAH; dichotomized into Σ(8)PAH(semivolatile) (MW 178-206), and Σ(8)PAH(nonvolatile) (MW 228-278), black carbon (BC), PM(2.5) (particulate matter) by floor level (FL), season and building type. We hypothesize that PAH, BC and PM(2.5) concentrations may decrease with higher FL and the vertical gradients of these compounds would be affected by heating season and building type. PAH, BC and PM(2.5) were measured over a two-week period outdoor and indoor of the residences of a cohort of 5-6 year old children (n = 339) living in New York City's Northern Manhattan and the Bronx. Airborne-pollutant levels were analyzed by three categorized FL groups (0-2nd, 3rd-5th, and 6th-32nd FL) and two building types (low-rise versus high-rise apartment building). Indoor Σ(8)PAH(nonvolatile) and BC levels declined with increasing FL. During the nonheating season, the median outdoor Σ(8)PAH(nonvolatile,) but not Σ(8)PAH(semivolatile), level at 6th-2nd FL was 1.5-2 times lower than levels measured at lower FL. Similarly, outdoor and indoor BC concentrations at 6th-32nd FL were significantly lower than those at lower FL only during the nonheating season (p < 0.05). In addition, living in a low-rise building was associated significantly with higher levels of Σ(8)PAH(nonvolatile) and BC. These results suggest that young inner city children may be exposed to varying levels of air pollutants depending on their FL, season, and building type.