A rail-car derailment on August 5, 2005, resulted in the release of approximately 45,000 l of sodium hydroxide (NaOH) into the Cheakamus River, 15 km north of Squamish, BC, Canada. Kick net and colonization basket sampling from August to December 2005 measured post-spill community structure, biomass and abundance of individual benthic invertebrates and compared them to pre-spill data, upstream controls and reference sites in the Georgia Basin. Community structure in the post-spill Cheakamus benthos was compared using the Canadian Aquatic Biomonitoring Network (CABIN) database and the Reference Condition Approach (RCA) along with multi-metric comparisons over time. Results showed benthos community structure in sites furthest downstream from the spill were most similar to the Reference Condition. Community structure, abundance and biomass recovery occurred within 3 months. Heptagenid mayflies and Chloroperlid stoneflies, appeared to have the highest sensitivity to sodium hydroxide effects. Relative rates of recovery across sites from various locations suggested downstream drift as a possible means of recovery. Results of these monitoring programs have provided insight into the response and recovery of freshwater benthic invertebrates to sodium hydroxide pulse disturbance and provide a surprising view of rapid recovery in affected invertebrate communities.