Two separate greenhouse esperiments were conducted to determine the effects of additions of a blue-green algae (Nostoc muscorum) to nutrient solution cultures with different rates of nitrogen fertilizer on the growth of lettuce (Lactuca sativa L. cv. Buttercrunch). Lettuce yields increased with increased rates of N. Yields were significantly greater in treatments containing 165 ppm N with N. muscorum culture added (at the rate of 33.3% by volume) than in treatments containing the same rate of N without N. muscorum. A similar growth increase was not noted at lower N. muscorum inoculation rates (16.7% by volume). These preliminary data indicate the potential for increased yields of lettuce grown under specific conditions in nutrient culture. Further research of the complex interactions within this biological equilibrium are required before specific application recommendations may be suggested.