Mass inoculation and computer clustering techniques were used in an abbreviated procedure to group similar bacteria isolated from four depths in the water column of Green Lake, Washington. Four groups of bacteria were differentiable and were categorized as orange-yellow Flavobacterium–Cytophaga, yellow Flavobacterium–Cytophaga, Vibrio–Aeromonas-, and Pseudomonas-like. Some of the groups were most prevalent incertain sample depths in the water column.