A psychrotrophic strain of Arthrobacter agilis, isolated from Antarctic sea ice, grows from 5 degreesC to 40 degreesC and in culture media containing 0-10% (w/v) NaCl. Maximum growth rate occurred at 30-35 degreesC with a drastic decline as the cultivation temperatures diverged. Adaptation to extremes of low temperature may be partially attributed to the production of the C-50 carotenoid bacterioruberin, and its glycosylated derivatives. Lowering of the cultivation temperature resulted in a concomitant increase in carotenoid production, which may contribute to membrane stabilisation at low temperature. Maximum biomass accumulation occurred at 5-30 degreesC with a tenfold reduction at 40 degreesC. Changes in growth rates were minimal in culture media containing 0-2% (,w/v) NaCl at 10 degreesC while a gradual decrease in growth rates occurred at higher salinity. Biomass accumulation at different salinity followed a trend similar to that observed with different cultivation temperatures. Maximum biomass accumulation was observed in culture media containing 0-5% (w/v) NaCl with a tenfold reduction at 10% (w/v) NaCl. Carotenoid production also decreased as salinity increased.