The aim of studies was to evaluate changes in the number of soil microorganisms 
as affected by soil heating. The experiment was carried out in plastic film greenhouses,
where tomato plants were cultivated. Total number of bacteria, actinomycetes, 
cellulolitic microorganisms, spore-forming bacteria and fungi was estimated. The indicator 
of biotic relations between total bacteria with actinomycetes and fungi was also calculated. 
Heating of the soil increased the number of bacteria, actinomycetes, and cellulolitic 
microorganisms, and decreased the number of fungi. The quantity of spore forming bacteria 
was not affected by heating. It is suggested that heating created more favourable 
conditions for biotic system establishment, better fertility and sanitary conditions.