A reported, but as yet unconfirmed, ill effect on fishes of wastes from a munition plant led to a study of the toxicity of these wastes to fishes. The red liquor from the manufacture of tri-nitro-toluene (T.N.T.) was suspected. The constituents of this waste include dissolved T.N.T. and toluene, both of which are very toxic. Many other compounds which may be very toxic are also present.