1) The document examines the effects of acute exposure to natural estrogen-containing soy extract on aggressive and courtship behaviors in adult male zebrafish. 2) Male zebrafish were exposed to vehicle control, synthetic estrogen (EE2), or two concentrations of soy extract (low and high) for 5 hours. 3) Results showed that exposure to soy extract, like synthetic estrogen, reduced aggressive and courtship behaviors in males, indicating possible negative impacts on reproductive success.