SYNOPSISThe time is ripe for protozoan ecologists to begin the general evaluation of the role of food quality in the energy transformations and materials flow in food webs involving protozoa and other small organisms. Current evidence suggests that major pathways of energy flow at any particular time depend upon the matches between prey species and consumers. There are 2 components to food quality related (informational) energy flow: (a) the information present in the molecular constitution of the prey; and (b) the ability of the protozoa to recognize and use it. If the evidence obtained from trophodynamic studies of 2 marine ciliates,Uronema marinumDujardin andEuplotes vannusMüller indicates a generalized ability of protozoa to regulate catabolic reactions to points which optimize energetic gains from their food, then it may be one of the keys to the evolutionary successes of the group