Aerosol concentrations and particle size distributions in three middle income homes were characterized over a three day period. Occupants of the homes were non-smokers. A single central sampling location between the kitchen and dining room areas was used in each of the homes. Thirty-seven and 47 mm prototype personal sampling inlets were collocated with two fixed PM10 dichotomous ambient samplers to determine the average concentration of particulate mass during daytime and evening-early morning sampling periods. Particulate concentrations in the three homes ranged from 14 to 42-mu-g m-3. On average, 37% of the particle mass was collected in a fine (2.5-mu-m aerodynamic diameter or below) fraction, 26% was observed in a coarse fraction between 2.5 and 10-mu-m, and 37% was found in a fraction greater than 10-mu-m. Particle concentrations obtained with prototype personal samplers compared reasonably well to those obtained with 10-mu-m ambient air dichotomous samplers. Aerosol size information obtained from automated aerosol instruments suggests that the most significant event for generating small particles in all of the households was cooking. Household vacuum sweeping was the most significant large particle generating event. Electron photomicrographs indicated that particles below 1-mu-m dominate the particle size-number distribution. Biological and mineral based particles predominantly make up the 2.5-10-mu-m size range.