The lettuce aphid, Nasonovia ribis-nigri (Mosley), arrived in California from Europe in 1998 and has become the primary arthropod pest of lettuce on the central California coast. The lettuce aphid contaminates lettuce by colonizing the newest leaves at the center of the plant. Conventional management of the pest requires frequent application of insecticides to suppress incipient populations. Organic lettuce growers rely on the activity of endemic natural enemies to suppress lettuce aphid populations. A naturally occurring complex of aphidophagous syrphid flies makes it possible to produce organic lettuce in the region. Many organic growers enhance the activity of syrphids by inter-planting lettuce with insectary crops such as sweet alyssum (Lobularia maritima). In order to improve understanding of this syrphid complex, a survey of syrphids on organic romaine was carried out in and around the Salinas Valley over a six month period. Syrphids were sampled under varied growing conditions, with and without the presence of insectary crops. Information on the role of different syrphid species in the complex will be used to improve the predictability of naturally occurring biological control of lettuce aphid in California.