Eleven enrichment cultures were developed by a "seeded" enrichment culture technique, and one was developed by a simple enrichment technique. The seeded enrichment, the pure "seed," and the simple enrichment cultures were compared during growth on mesquite wood, cotton, carboxymethylcellulose, and cellobiose. All of the enrichment cultures were cellulolytic and exceeded the pure seed cultures in mesquite wood hydrolysis and/or viable cell count. Yeast extract improved, but was not essential for, growth of the seeded enrichment cultures on carboxymethylcellulose. Two of the seeded enrichment cultures, CAD5 and CAD11, grew best at 37 degrees C and pH 7.0 on mesquite wood. A 1.0% (wt/vol) wood concentration was optimum for their growth.