The tensile test of unnotched and round specimens in the liquid tin, lead, zinc and bismuth bath was carried out with an Instron type testing machine in order to investigate the susceptibility of a mild steel to liquid metal embrittlement for which some inconsistent results had been reported among investigators. In the present paper, in this context, various effects of test conditions on liquid metal embrittlement were studied.The results obtained are summarized as follows;(1) Propensity to liquid metal embrittlement is influenced by the test temperature, for which the optimum temperature exists.(2) The embrittlement is greatly affected by the strain rate, for which the optimum rate also can be found.(3) It is not considered that liquid metal embrittlement is essentially influenced by the holding time at the testing temperature before straining.(4) The embrittlement by liquid zinc is very sensitive to the surface roughness of the specimen, that may be ascribed to the notch effect.(5) The embrittlement by liquid tin has no relation with the diameter of specimen or the ratio of surface area to volume of test specimen.(6) Liquid bismuth does embrittle the mild steel.Consequently, it is not considered that the embrittlement in liquid metal of mild steel is merely controlled by the chemical diffusion that depends upon the acting time and temperature.