Pure cultures of coliform bacteria were inoculated into lactose broth and brilliant green bile broth. Tubes were examined at intervals of 30-45 min. Immediately following the appearance of gas in the inner tube, portions were plated for colony counts. Population figures, based on 780 observations, coincident with initial gas production ranged from 40,000,000-390,000,000 per ml. B. G. B. figures were higher than those for lactose.