Construction workers' exposure to airborne viable mycobacteria was studied during the remediation of three moldy and two nonmoldy buildings. Furthermore, the concentrations of airborne fungal and actinobacterial spores were determined. The samples for the microbial analyses were collected using a six-stage impactor and an all-glass impinger sampler, and by filter sampling. Specific mycobacteria media and nonselective media were used for the cultures. The samples were cultured for the total numbers of rapidly growing and slow-growing mycobacteria, and the isolates obtained were identified to the genus or species level. Mycobacteria were recovered from the air during the remediation of two of the moldy buildings and one nondamaged building. Concentrations of mycobacteria up to 160 cfu/m3 were detected. A total of 43 mycobacterial isolates was recovered. Most of the isolates were slow-growers, only two rapid-growing strains being detected. The 38 identified isolates belonged to potentially pathogenic species, including Mycobacterium avium complex, M. scrofulaceum, and M. fortuitum, and to saprophytic species, including M. nonchromogenicum and M. terrae. Mycobacteria were the most often detected in samples taken with a six-stage impactor. They were found in buildings with both high and low concentrations of fungi. In conclusion, mycobacteria, both potentially pathogenic and saprophytic species, may be released into the indoor air during the remediation of buildings.