Groups of twenty rats were given weekly subcutaneous injections of one of the food colours Brilliant Blue FCF, Blue VRS, and Green S. The dose, 20 mg in isotonic saline, was given for 45 weeks after which the rats were observed for an additional 26 weeks. There was ulceration and abscess formation at the site of injection in rats given Blue VRS. The other two colours produced no noticeable local or systemic effects. No subcutaneous fibrosarcomas were seen in any of the rats. Two rats given Blue VRS developed rhabdomyosarcomas in the area of the injection site. This finding is being investigated.