Toxicological monitoring was conducted on an estuarine marshland in the Houston Ship Channel following a local oil spill. Acute toxicity of petroleum-contaminated sediments, as determined by the Microtox Bioassay, was used to monitor intrinsic recovery of the impacted marsh. Sediment toxicity was determined by performing the Microtox 100% test on elutriates from wet sediment samples collected over a 7-month period following the spill. Toxic responses were examined for spatial and temporal relationships and were compared to various parameters of interest, including total petroleum hydrocarbon (TPH), total extractable materials (commonly referred to as oil and grease [O&G]), and GC/MS-quantified total saturates and aromatics. Toxicity was randomly distributed within the study site and decreased with time. Acute toxicity was correlated with TPH measurements and moderately correlated with GC/MS-quantified saturate concentrations. However, toxicity levels were not correlated with O&G or GC/MS aromatic summations.