TRI Reagent LS is a quick and convenient reagent for use in the simultaneous isolation ofRNA DNA and proteinfrom liquid samples of human animal plant yeast bacterial and viral origin. A convenient single-step liquid phase separation results in the simultaneous isolation of RNA DNA and protein. This procedure is an adaptation of the singlestep method reported by Chomczynski and Sacchi for total RNA isolation and permits fast and efficient processing of liquid samples. TRI Reagent LS performs well with large or small sample volumes and many samples can be simultaneously extracted.TRI Reagent LS is a mixture of guanidine thiocyanate and phenol in a monophase SOLUTIONon. When a biological sample is homogenized or lysed with it and chloroform or 1-bromo-3-chloropropane is added the mixture separates into 3 phases an aqueous phase containing RNA the interphase containing DNA and an organic phase containing proteins. Each component can then be isolated after separating the phas