The occurrence of Legionellae bacteria in the hot water distribution systems of seven apartment and commercial buildings located in different parts of Riga city (Latvia) was studied. Hot water samples with temperature from 25 to 50 oC were taken from taps in the morning hours during four month period. Legionellae were isolated on culture media and confirmed with fluorescence in situ hybridization technique using peptide nucleotide probes targeting 16 rRNA. Legionella pneumophila was found in 62% of water samples. This is a first study showing occurrence of Legionellae in hot water supply systems in Latvia.