The study of messenger RNA in mammalian cells by Northern analysis requires the extraction of intact RNA in pure form. Although a number of reliable techniques have been developed for the purpose, most are fairly complex, involving steps such as ultracentrifugation and multiple extractions with large volumes of phenol and chloroform. When the number of cell samples to be analyzed is large, these techniques can be unwieldy. I now describe an RNA purification procedure which is simple enough to allow handling of a large number of cultured cell samples. It uses safe and inexpensive reagents and produces a high yield of pure total cell RNA, essentially free of DNA and ribonuclease, suitable for Northern analysis. The procedure also allows extraction of intact RNA from human granulocytes, cells which are rich in ribonuclease and contain very low amounts of RNA.