The paper describes the fractionation of high-molecular-weight RNA using polyacrylamide-gel electrophoresis. The method involves preparing gels with recrystallized acrylamide and bisacrylamide, and electrophoresis in tris-sodium acetate-EDTA buffer. The mobility of RNA is inversely related to its sedimentation coefficient and varies with gel concentration. Electrophoresis in 2-2% to 2-6% gels provides a fractionation similar to density-gradient centrifugation, resolving ribosomal RNA components, transfer RNA, and minor components. In 5% and 7-5% gels, 4s and 5s RNA are separated, and ribosomal RNA is excluded. The resolution is greater and more detailed than with centrifugation, allowing for simultaneous and rapid analysis of many samples. Polyacrylamide-gel electrophoresis, which has been successful in protein fractionation, has been less used for RNA. Separations of smaller RNA molecules have been described, and the method is now being used for separating 5s from 4s RNA. The problem of RNA sticking to the gel surface has been overcome by using purified reagents and thorough deproteinization. The gels are now sufficiently transparent for ultraviolet scanning. The methods involve recrystallizing acrylamide and bisacrylamide, preparing gels with specific concentrations, and electrophoresis in appropriate buffers. The gels are scanned for ultraviolet absorption and radioactivity. The results show that RNA components such as 28s, 18s, 4s, and 5s RNA can be separated with high resolution. The method allows for the separation of RNA components with high precision and is more efficient than density-gradient centrifugation. The paper also discusses the effects of impurities, the separation of different RNA species, and the potential for using this method in preparative separations. The method is compared to other techniques and is suggested as a convenient alternative for analytical purposes. The paper concludes that polyacrylamide-gel electrophoresis provides a valuable tool for the fractionation of RNA.The paper describes the fractionation of high-molecular-weight RNA using polyacrylamide-gel electrophoresis. The method involves preparing gels with recrystallized acrylamide and bisacrylamide, and electrophoresis in tris-sodium acetate-EDTA buffer. The mobility of RNA is inversely related to its sedimentation coefficient and varies with gel concentration. Electrophoresis in 2-2% to 2-6% gels provides a fractionation similar to density-gradient centrifugation, resolving ribosomal RNA components, transfer RNA, and minor components. In 5% and 7-5% gels, 4s and 5s RNA are separated, and ribosomal RNA is excluded. The resolution is greater and more detailed than with centrifugation, allowing for simultaneous and rapid analysis of many samples. Polyacrylamide-gel electrophoresis, which has been successful in protein fractionation, has been less used for RNA. Separations of smaller RNA molecules have been described, and the method is now being used for separating 5s from 4s RNA. The problem of RNA sticking to the gel surface has been overcome by using purified reagents and thorough deproteinization. The gels are now sufficiently transparent for ultraviolet scanning. The methods involve recrystallizing acrylamide and bisacrylamide, preparing gels with specific concentrations, and electrophoresis in appropriate buffers. The gels are scanned for ultraviolet absorption and radioactivity. The results show that RNA components such as 28s, 18s, 4s, and 5s RNA can be separated with high resolution. The method allows for the separation of RNA components with high precision and is more efficient than density-gradient centrifugation. The paper also discusses the effects of impurities, the separation of different RNA species, and the potential for using this method in preparative separations. The method is compared to other techniques and is suggested as a convenient alternative for analytical purposes. The paper concludes that polyacrylamide-gel electrophoresis provides a valuable tool for the fractionation of RNA.