Salted and dried fish(Nemipterus virgatus)acquired from Hong Kong, was treated with 0.43–110 mM nitrite duringin vitrodigestion using gastric enzymes and the volatileN‐nitrosamine content and mutagenicity onSalmonella typhimuriumTA 100 assayed without concentration.N‐Nitrosodimethylamine (NDMA; the only nitrosamine detected) formation was second order in nitrite concentration. When 10 g of fish was treated with 6.96 nM nitrite, 394 nM NDMA was formed. Thiocyanate was catalytic for NDMA formation at nitrite concentration >0·87 mM and when the ratio of thiocyanate to nitrite was > 1. Approximately a 50% inhibition in NDMA formation by ascorbic acid was seen when the ratio of ascorbate to nitrite was approximately 2 or greater and the nitrite concentration was 1.74 mM. Mutagenicity increased with increasing nitrite concentration but the addition of thiocyanante did not increase mutageneicity over nitrite alone. Ascorbate increased mutagenicity even though NDMA formation was inhibited. Even at nitrite concentrations > 100‐fold higher than expectedin vivothere was insufficient NDMA formed to account for the observed mutagenicity. These data do not exclude the possibility that the observed mutagenicity was due to non‐volatileN‐nitroso compounds, however, this possibility seems unlikely given the effects of ascorbate and thiocyanate which would be expected to inhibit and enhance non‐volatileN‐nitroso compound formation.