Colon adenocarcinoma-associated chromosomal nonhistone proteins were determined in rat colon adenocarcinoma chromatin and in colon chromatin of Sprague-Dawley rats treated with 1,2-dimethylhydrazine (DMH) by the enzyme-linked immunosorbent assay method. The specific nuclear proteins are tissue-specific oncofetal antigens. They were also detected in fetal rat colon chromatin but not in adult rat colon chromatin. The specific tumor-associated nonhistone proteins were identified by immunoblot. The molecular weight ranges of these proteins were 79,000 89,000 and 40,000–56,000 daltons. Administration of DMH to Sprague-Dawley rats induced colon tumor and colon tumor-associated nonhistone proteins in the chromatin. However, DMH failed to induce colon tumor and tumor-associated nonhistone proteins in Lobund-Wistar rat