Atomic force microscopy (AFM) has been used to study the translocation involving chromosomes 11 and 13. An amniocentesis procedure was performed at 18 weeks of pregnancy on a familial balanced translocation carrier mother whose karyotype was 46,XX,t(11; 13) (q23;q34). After harvesting the tissue cultures, light microscopy studies (LM) have indicated that the fetus had the same translocation. A 0.3 mum gap region on the derivative chromosome 13 was determined by AFM; it was equivalent to a mid-sized G-band. The enhanced resolution of AFM with respect to its line measure analysis and three-dimensional image capture capability has allowed an extension and reconsideration of conclusions about chromosomal aberrations based on the study of LM preparations. In this manner, chromosomal disorders will be studied at nanoscale to help in the planning of new therapy strategies.