During February 1979 to December 1982 we studied the karyotype of 706 psychiatric adult patients without making a clinical selection. We found a chromosomial mosaïc aberration in 37 cases, concerning one leukocyte mitosis for ten studied cells : so a proportion of 5.2% cases. There do not exist statistics concerning the general population's mosaïc aberrations but in the same population the proportion of the homogeneous aberrations is near 0.5%, so 10 times lower than the proportion that we observed. The largest number of aberrations found concern the gonosomes, essentially some monosomics 45,XO or some trisomics 47,3X, among women who present a maniac depressive psychosis or another type of depression.