Observations have been made during both cloudy and sunny weather on the body temperatures of the glass lizard Ophisaurus apodus in Yugoslavia. The results indicate that during sunny weather this species is heliothermic elevating its body temperature to around 30°c. When the weather was cloudy glass lizards were observed abroad on grass covered clearings but body temperatures were significantly lower during cloudy weather than those recorded under sunny weather. There was no significant difference between body temperatures measured during sunny weather in May and sunny weather in September and October. The body temperatures of males, females and juveniles were not significantly different during sunny or cloudy weather. For most of the daily period there was little difference between body temperatures except between 1700-1900 hrs when they were significantly lower. In general, the body temperatures of field measured 0. opodus were lower than those recorded from animals in laboratory heat gradients (Cherchi, 1961; Hailey, 1984).