DNA ploidy patterns in cell nuclei from cytologic and histologic samples will be used to provide tumor diagnostic and prognostic information. Our rapid, computer-controlled, video-based microphotometer system allows the recording of DNA-ploidy patterns within minutes, with statistically valid sample sizes, thus making this valuable method practical as a routine clinical laboratory test. It is intended to standardize the methodology for this purpose, to assemble and examine a clinical database to correlate ploidy patterns with clinical implications, to establish objective measures for ploidy pattern evaluation, and to establish the sensitivity for the detection of aneuploidy. An inexpensive, microprocessor-based microscope attachment and graphic display has been designed as a prototype for a practical pathology laboratory instrument. (3)