Abstract –Retention of Cu and Zn in the mouth after rinses with known volumes of aqueous solutions of the metal salts was measured by atomic absorption. The mean amounts retained in 10 subjects were 0.02 mg Cu and 0.22 mg Zn. These values represent approximately 31 % of the Cu and 15% of the Zn originally in the rinse. The intraindividual variation (s.d.), estimated by three mouthrinses at weekly intervals in three subjects averaged 2.1% for Cu and 2.3% for Zn. Following a rinse the salivary concentration of Cu and Zn decreased rapidly during the first 4 h, approaching premise level