The use of s-collidine (2,4,6-trimethylpyridine) as a buffer for fixatives in electron microscopy was first described by Bennett and Luft (1959). Since the s-collidine contained impurities, a method was described for its purification, involving crystallization, refluxing and distillation, that made the process long and tedious. Although s-collidine of high purity can be purchased (Eastman Organic Chemicals, Polysciences), it is expensive. These facts have probably discouraged many investigators from using this compound routinely as a buffer. The procedure to be described has simplified the purification of s-collidine to filtration through a column of activated basic aluminum oxide.