BACKGROUND: Excess moisture and visible mold are associated with increased risk of asthma. Only a few studies have performed detailed home visits to characterize the extent and location of moisture damage and mold growth. METHODS: Structured home inspections were performed in a birth cohort study when the children were 5 months old (on average). Children (N = 398) were followed up to the age of 6 years. Specific immunoglobulin E concentrations were determined at 6 years. RESULTS: Moisture damage and mold at an early age in the child’s main living areas (but not in bathrooms or other interior spaces) were associated with the risk of developing physician-diagnosed asthma ever, persistent asthma, and respiratory symptoms during the first 6 years. Associations with asthma ever were strongest for moisture damage with visible mold in the child’s bedroom (adjusted odds ratio: 4.82 [95% confidence interval: 1.29–18.02]) and in the living room (adjusted odds ratio: 7.51 [95% confidence interval: 1.49–37.83]). Associations with asthma ever were stronger in the earlier part of the follow-up and among atopic children. No consistent associations were found between moisture damage with or without visible mold and atopic sensitization. CONCLUSIONS: Moisture damage and mold in early infancy in the child’s main living areas were associated with asthma development. Atopic children may be more susceptible to the effects of moisture damage and mold.