1. Influence of temperature on electrically evoked twitch contractions and maximal voluntary contractions was studied in human first dorsal interosseus muscle. The range of the muscle temperature was 35-12 degrees C. 2. The maximal twitch tension decreased by about 50% in cooling from 35-12 degrees C; the tension decrease was more pronounced below 25 degrees C. The temperature coefficients (Q10 values) estimated for muscle temperatures of 35-25 degrees C were 1.43 for time-to-peak and 1.7 for half-time of relaxation. 3. The maximum voluntary tension remained relatively constant on cooling to 25 degrees C but decreased by about 30% on cooling to 12-15 degrees C. The normalized rate of tension rise in voluntary contractions was largely independent of temperature. 4. Results are discussed in relation to previous work on temperature and muscle contraction in humans and in animals.