Results obtained by examination of 22 human cases suspected for drowning, one human case of death other than drowning and several tests on laboratory rats were used as a basis for evaluation of diatom method as supportive in forensic expertise of drowning. The recovery of diatoms from various examined organs, their qualitative and quantitative composition, if properly treated without the possibility of contamination, can be a reliable proof of the time and place of drowning. The priority of organ examination (external microflora determination, lungs, brain, heart (and/or blood), stomach, liver and kidney, and finally bone marrow) is discussed and established as well as the basic future research on cases suspected of drowning, but also on non-drowned victims and laboratory animals.