The advent of molecular genetic techniques has brought forth new procedures for in situ chromosomal analysis. One of these techniques is the primed in situ labeling (PRINS) procedure which constitutes a fast and efficient alternative to conventional fluorescence in situ hybridization (FISH) for chromosomal detection. Based on the use of chromosome-specific primers, the PRINS method combines the high sensitivity of the PCR reaction with the cytological localization of DNA sequences. Using this approach, numerous cytogenetic applications have been successfully developed on various types of cells. With the development of rapid protocols producing reliable and reproductible results, the PRINS procedure has an enormous potential for cytogenetic investigations.