The present invention provides for a method of drying and spreading chromosomes from various biological samples to yield optimal chromosomal spreading. The method requires preparing a biological sample for treatment, providing a cytogenetic chamber capable of setting predetermined conditions, pre-testing a portion of the biological sample in the cytogenetic chamber, and finally treating the remaining biological sample. The method is useful to yield metaphase chromosomes that are small and rounded, with very few overlapping or scattered chromosomes. Furthermore, the method is uses restricted ranges of temperature and relative humidity to achieve consistent chromosomal spreading. The morphologies of the chromosomes are preserved in order to execute banding techniques at 550 bands and chromosomal analysis on high-resolution chromosomes.