Samples of house dust from 18 flats in Warsaw (Poland) were collected from five environments: floor, shelves with books, kitchen, bathroom, and bed. Penicillium, Aspergillus, Cladosporium and Alternaria were the most common genera identified in house dust samples. The highest culturable fungal concentrations were recorded in dust from shelves (median value 8.2 × 104 CFU/g of dust) and the least one from beds (median value 8.0 × 103 CFU/g of dust). Differences in CFUs between environments were statistically significant for Penicillium, Aspergillus and Alternaria. Concentration of Penicillium and Aspergillus was significantly higher in autumn than in spring whereas concentration of Cladosporium was significantly lower in autumn than in spring. Efficiency of ventilation in bathroom had significant effect on Cladosporium counts. Certain relationships between concentration of culturable fungi and some customs of occupants were illustrated.