Аннотация:We present the results of a study of the dependence of the “red leak” of the filters U and B from the color index V - R of stars and the interstellar reddening. A comparison of filters with diherent red leak contributions is made. The error arising from the undercounting the red leak in the case of the U filter used on the 0.6-m telescope of the CMO SAI can be up to 0.6-0.8m for stars of late spectral types with large interstellar reddening. The results of observations of four red stars in the UBVRcIc bands and corrections to account for red leak are presented.