Municipal effluents are known to release a variety of contaminants that have the potential to compromise neuroendocrine signaling pathways in aquatic organisms. The purpose of this study was to examine the hepatic and reproductive toxicity of a physically-chemically treated effluent to adult fathead minnows following 21 days of exposure at 25 ^oC. The following biomarkers were determined after the exposure period: oxidative stress (lipid peroxidation and DNA damage), estrogenicity (vitellogenin and glucose-6-phosphate dehydrogenase) and energy budget (mitochondrial electron transport, total sugars and lipids in the liver). Reproductive function was also determined by observation of secondary sexual characteristics, egg production and hatching. The results revealed that fish exposed to municipal effluent had increased levels of hepatic vitellogenin, higher energy expenditure (electron transport activity in mitochondria) and increased levels of lipids and sugars in the liver. The only observed changes in reproduction were decreased egg production and slight discoloration of males. Egg production was negatively correlated with lipid peroxidation in gills and total lipids in the liver. Vitellogenin also contributed significantly to energy expenditure in the liver, suggesting that energy reserves and oxidative stress were involved in decreased egg production. Analysis of the eggs revealed that the exposed eggs had lower lipid content and higher sugar content compared to the control eggs. The study supports the hypothesis that exposure of fish to high concentrations of effluent discharges (>20%) could have detrimental effects on energy expenditure, egg production and egg energy content which impact their reproduction.