Taurine increases force production in skeletal muscle, and taurine levels may fall during exercise. The contractile properties and fatigability of extensor digitorum longus (EDL) muscles depleted of taurine by guanodinoethane sulfonate (GES) treatment were investigated. GES treatment decreased muscle taurine levels to <40% of controls. Peak twitch force levels were 23% of controls in GES treated EDL muscles (p < 0.05), but maximal specific force was unaffected. The force-frequency relationship was examined and significantly less force was produced by the GES treated muscles compared to controls at stimulation frequencies from 50 to 100 Hz (p < 0.05). GES treated EDL muscles exhibited significantly slower rates of fatigue than controls (p < 0.05). In skinned fibres, 20 mM GES had a small but significant effect on force production, indicating that GES may have some minor taurine-like effects. In this study, a fall in taurine levels decreased force output, and increased the endurance of EDL skeletal muscles.