In the given article are discussed the results of the investigations and elaborating of the studies of character of radioactivity of sedimentary deposits of dicteenomous schists in Leningrad district. Here is treated also a theorie of genesis of radioactivity of dicteenomous schists. It was stated: a) Measure of dicteenomous schists differs from the other sedimentary rocks by the higher degree of radioactivity. b) Distribution of the radioactive substances in the shale measure is not uniform in the vertical cut of measure as well as in the direction of the strike. c) Thickness of the slices, containing the radioactive substance in different sections, varies considerably and reaches, as to the results of approbation, tens of centimeters. There are also some others results deducted.