Total RNA was extracted from the chorioallantoic membrane (CAM) of Sendai virus-infected chick embryos by the original Kecskeméthy-Schäfer method and by a modification of this technique, including phenol treatment, in order to ensure complete removal of proteins. The purity of the total RNA extracted by the modified technique was ascertained by spectral analysis. Chromatography on oligo(dT)-cellulose of the total RNA led to the isolation of poly(A)-rich mRNA--the material retained by oligo(dT)-cellulose and eluted with the buffer of the lowest ionic strength. The ability of the poly(A)-rich mRNA thus obtained to stimulate incorporation of 14C-leucine into protein was demonstrated in a cell-free protein-synthesizing assay system.