ABSTRACT.The increases above control of oxygen uptake (&Dgr;&OV0312;o2) and temperature (&Dgr;Tm) of the dog gastrocnemius‐plantaris muscle preparationin situwere determined during the last minute of 5 minutes of twitch contractions at 0.5,1,2,3,5 or 10/sec or of tetanic contractions (40/sec, 200 msec) at 12,20,40 or 60/min. The &Dgr;Tmincreased from .29 ± .07 to 1.54 ± .28 C° (mean ± standard error) with increasing twitch frequencies and from .70 ± .17 to 1.60 ± .22 C° with tetanic contractions. The &Dgr;&OV0312;o2increased to a peak of 139.7 ± 14.4 &mgr;l/g min at 5/sec during twitches but increased from 35.9 ± 4.1 to 104.0 ± 8.3 &mgr;l/g min with increasing tetanic frequencies. The &Dgr;Tmcaloric equivalent accounted for 23 to 40% of the &Dgr;&OV0312;o2caloric equivalent during twitches and for 51 to 63% with tetanic contractions. Differences in blood flow partially explain the different percentage ranges calculated. These low percentages limit the usefulness of &Dgr;Tmas an indicator of &Dgr;&OV0312;o2but since &Dgr;Tmincreases with contraction rate it can be used to indicate relative metabolic rates.