Interlaboratory quality assurance studies have been conducted for DNA flow cytometry, but not for DNA image analysis systems. The purpose of this study was to investigate if concordance of DNA image analysis systems existed with respect to classification and staining of standardized material. In three separate rounds, human liver cells were measured randomly by means of the image cytometry system present in each participating laboratory. The features integrated optical density (IOD) and AREA were reported. The relationship between the coefficient of variation (CV) of the 2c and 4c peak were compared with three models. In the three rounds the number of participating laboratories was 11, 14 and 11, respectively. Sequential plotting of normalized IOD values yielded useful information about intra-measurement variation. Comparison of measurements in specimens stained in the participating and central laboratory revealed similar CV values. In general, the precision of the instruments, expressed as the 4c/2c and 8c/2c ratios was good. The accuracy of the different laboratories expressed as the CV of IOD for the three rounds varied from 2-17%. The relation of the CVs of the 2c and the 4c peaks was best fit with the model of the addition of two normal distributions. We conclude that interlaboratory comparison of DNA measurements performed on different instruments is certainly feasible and could facilitate improvement in quality standards.