A simple technique which results in good quality early mitotic stages of amniotic fluid (AF) cells is presented. Two days after trypsinization AF cell cultures are incubated for 4 h in culture medium containing 20 U/ml liquemin. During the last hour 5 micrograms/ml ethidium bromide (EB) is added and 15 min before harvest 0.04 micrograms/ml colcemid is applied as usual. G-banded and Q-banded chromosomes corresponding to at least 550-850 bands per haploid genome can be obtained in sufficient numbers.