A tissue-culture assay method is described for the evaluation of the toxicity of substances of extremely limited solubility in aqueous solutions. It is a modification of the powder-application method used in Part I of this paper, the main difference being the counting of cells in the lag phase rather than in the replication phase. Several metals used in orthopaedic implants and shown to be well tolerated in tissues clinically are shown to have significant toxicity for tissue culture cells, the cobalt chromium alloys being more toxic than the stainless steels of type 316. Tissue-culture cells containing material derived from the alloys (corrosion products) were observed in mitosis and cells so labeled survived as many as fifteen sequences of subculture.