We used radio telemetry to evaluate activity area size, habitat use, diurnal activity, and the influence of weather, environmental temperatures and sex on daily movements in 18 Sternotherus odoratus in southwestern Michigan. Turtles mainly moved within the highly vegetated littoral zone but two individuals used wet meadow areas adjacent to the lake and an adjoining stream. Activity area size, as measured by the 95% fixed kernel method using 40 radio telemetry days per individual, did not vary between the sexes. Mean total daily distance moved (TDDM) over a 12 h time period averaged 27 m and was not influenced by sex or by variation in daily weather conditions. However, seasonal changes in environmental temperatures were positively correlated with mean daily shell temperature (T_s) and TDDM indicating limits on activity on relatively cool days. While turtles were found to move at any time over the course of a day, distances moved during six, 4 h intervals over a 24 h period were greatest during the late morning and late afternoon. Mean T_s was greatest during the afternoon but did not differ between the sexes and mean T_s was similar to prevailing water temperatures indicating that bimodal activity was probably not dictated by diel variation in temperature.