A tank study was conducted to determine the effects various concentrations of crude oil on brackish marsh plants. Scirpus olneyi and Spartina patens were grown in tanks and subjected to a light and a heavy crude oil at four concentrations and four water levels over an H.5-month period. Growth and survival ofplants were detennined monthly. A fluctuating water level (+5 to -5cm) with so parts per thousand (ppt) of heavy crude oil was the treatment most detrimental to S. olneyi. Crude oil enhanced growth and survival of S. olneyi at a water level of +5cm above the soil surface. Growth increased as oil concentrations increased and was greater for heavy oil than for light oil of equal concentrations. For S. patens treated with crude oils, a fluctuating water level (+5 to -5cm) and a +5cm water level were the most detrimental. High oil concentrations were detrimental to S. patens at water levels of -5cm and 0em. Damage to S. patens was more severe for heavy oil than for light oil. As oil concentrations increased, damage was more evident.