Indoor mould growth can affect health, especially in early childhood. As part of a birth cohort follow-up, the purpose of this study was firstly to examine spectrum and levels of airborne fungi in 190 Paris newborns' dwellings, and secondly to identify predictors of these levels. Sequential duplicate air samples were collected twice a year in the newborn's bedroom and outside the building. A single-stage multi-holed impactor (Air Ideal) was used with chloramphenicol/MEA agar. Housing characteristics were assessed using a questionnaire administered by a trained interviewer. Cladosporium and Penicillium were isolated in, respectively, 77% and 93% of homes in the cold season, and in 95% and 83% of homes in the hot season. Aspergillus and Alternaria were recovered from indoor air in, respectively, 60% and less than 20% of homes. Geometric means (geometric standard deviation) of indoor total airborne fungal concentrations at two different visits were, respectively, 232.4 (3.2) and 186.7 (2.7)cfu/m(3). In the GEE multivariate analysis, outdoor fungal concentrations were the best predictors for variability of indoor total fungal and Cladosporium concentrations (respectively, R(2)=32% and 31%). Levels of total airborne fungal and Cladosporium concentrations were significantly higher during the hot season (respectively, p=0.003 and p<0.001) and were positively correlated with the duration of bedroom aeration (respectively, p=0.004 and p<0.001). Signs of dampness were associated with higher total airborne fungi (p=0.031) and Aspergillus levels (p=0.055). This study provides for the first time indoor airborne fungal spectrum and concentrations in Paris. Outdoor levels and season largely contributed to the variability of indoor total airborne fungal concentrations, which also depended on aeration and signs of dampness.