A method for isolation of large, translationally active RNA species is presented. The procedure involves homogenization of cells or tissues in 5 M guanidine monothiocyanate followed by direct precipitation of RNA from the guanidinium by 4 M LiCl. Modifications are described for use with tissue culture cells, yeast, tissues, or isolated nuclei. The advantages of the procedure include speed, simplicity, avoidance of an ultracentrifugation, and its applicability to large numbers of small samples. The procedure yields large mRNA precursors up to 10 kb and mRNA species which translate very well. However, small (less than 300 nucleotides) RNA species are recovered with a poor yield.