Aneuploidies of chromosomes 13, 18, 21, X and Y account for up to 95% of liveborn chromosomal abnormalities. While conventional cytogenetic analysis requires 1-3 weeks for providing a result, Fluorescence in situ Hybridization (FISH) on uncultured amniotic fluid enables rapid diagnosis (48 h) of most common numeric aneuploidies. FISH technique, as a tool for prenatal diagnosis, was carried out in 7 high risk pregnancies. Analysis was performed on uncultured amniotic fluid samples using commercially available probes for centromere regions of chromosomes 18, X and Y and for the 13q14/21q22 region. Our analysis indicated that all the samples had a normal number of observed chromosomes which was also confirmed by conventional cytogenetics analysis. The aim of this work was to develop and apply FISH for rapid and simultaneous prenatal detection of most common aneuploidies.