In an attempt to determine the relationship between the features of houses and moulds growing indoors, 242 houses were examined in Izmir, a city on the west coast of Turkey with a mild climate. During house visits a questionnaire was given and air was sampled using an 'air IDEAL' air sampler for quantitative fungal culture. The moulds most commonly isolated were Aspergillus, Penicillium, and Mucor spp. Aspergillus growth in houses older than 20 years was more common than other species when the features of houses and isolated fungi were compared. Mucor grew significantly more in houses where the air was humid, the temperature was cooler and there were pot plants. Penicillium grew more frequently in houses where visible mould was present and birds were bred. However, no relationship could be demonstrated between the method of heating, the number of household members, exposure to sun, type of building and flooring with a specific mould. As a conclusion, many household factors suggested as risk factors for mould growth have been examined and only a few relationships could be established between certain features of houses and moulds. However, mould growth is much affected by many conditions and the environment in a house is one of many factors that may facilitate growth.