Identification of chromogenic gram-negative bacilli on the basis of pigment production as a taxonomic criterion is unreliable. Because of this, a wide range of morphological, cultural and biochemical characteristics of bacteria in this category was examined. The salient features found to be useful for identification of pigmented bacilli, including Flavobacterium, Xanthomonas, the fluorescent pseudomonads, Pseudomonas cepacia, P. stutzeri, P. maltophilia, P. putrefaciens, and Group VE, are reviewed.