AbstractTumor DNA content was determined by flow cytometry in 24 surgically resected specimens from patients with primary lung cancer to compare results from fresh and paraffin‐embedded specimens. We found a good correlation in DNA indices between fresh and paraffin‐embedded specimens (r=.978), although one tumor with DNA near‐diploidy was mistaken as DNA diploid in paraffin‐embedded specimens. In the measurements of paraffin‐embedded specimens, eight of 24 tumors were DNA multiploid and showed DNA content heterogeneity. These results indicate that DNA content analysis of paraffin‐embedded specimens is helpful because it makes it easy to analyze multiple specimens from different parts o