A newborn infant with clinical and pathological findings typical of trisomy 13 and 22 syndromes had an extra chromosome which was a derivative chromosome from maternal balanced translocation affecting Nos. 13 and 22; 47,XY,+der(22), t(13:22)(q22:q12)Mat. The presence of extra specific euchromatic regions of No. 13(13q22 and/or 13q34) and No. 22(22q11) seem to be responsible for the trisomy 13 and 22 syndromes.