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Cylindrospermopsis raciborskii is a potentially toxic freshwater cyanobacterium that can tolerate a wide range of light and temperature. Due to climatic changes, the interaction between light and temperature is studied in aquatic systems, but no study has addressed the effect of both variables on the saxitoxins production. This study evaluated the combined effect of light and temperature on saxitoxins production and cellular quota in C. raciborskii. Experiments were performed with three C. raciborskii strains in batch cultures under six light intensities (10, 40, 60, 100, 150, and 500 mol of photons m(-2) s(-1)) and four temperatures (15, 20, 25, and 30 degrees C). The growth of C. raciborskii strains was limited at lower temperatures and the maximum growth rates were obtained under higher light combined with temperatures equal or above 20 degrees C, depending on the strain. In general, growth was highest at 30 degrees C at the lower light intensities and equally high at 25 degrees C and 30 degrees C under higher light. Highest saxitoxins concentration and cell-quota occurred at 25 degrees C under high light intensities, but were much lower at 30 degrees C. Hence, increased temperatures combined with sufficient light will lead to higher C. raciborskii biomass, but blooms could become less toxic in tropical regions.