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Anthraquinones are the largest group of the naturally occurring quinones. Both natural and synthetic anthraquinones are widely used in medical preparations, colourants in foods, hair dyes and others. Chrysazin (1, 8-dihydroxy-9, 10-anthracenedione; Figure 1) is a synthetic anthraquinone with 1, 8-dihydroxy groups like other natural anthraquinones such as emodin and chrysophanol which have been demonstrated to be mutagenic (Brown, 1980; Tikkanen et al., 1983). This chemical has been employed as an important dye material in textile industries. Mutagenicity of chrysazin has been reported in strains of TA1537 (Brown & Dietrich, 1979) and TA2637 (Tikkanen et al., 1983) of Salmonella typhimurium. We demonstrated the genotoxicity of this compound in the hepatocyte primary culture /DNA repair test (Mori et al., 1984). This communication is a preliminary report showing that the chemical is capable of inducing intestinal tumours in rats following oral administration. Two groups of male ACI rats, two months old, were used in this study. Rats of this strain have been maintained as an inbred line at our laboratory. Group I.-Eighteen rats were fed a basal diet containing 1% chrysazin (JAPAN CLEA Inc., Tokyo, Japan) throughout the experiment.