The article presents a new research protocol for evaluating temperature regulation in small field-active ectotherms, particularly lizards. It highlights the importance of understanding how accurately and effectively ectotherms regulate their body temperatures. The protocol requires data on body temperatures (Tb), available operative temperatures (Te), and the thermoregulatory set-point range (Tset). These data are used to estimate three quantitative indexes: the precision of body temperature (variance in Tb), the accuracy of body temperature relative to the set-point range (average difference between Tb and Tset), and the effectiveness of thermoregulation (how close Tb is to Tset compared to Te). The study also discusses how additional data on the thermal dependence of performance can be used to estimate the impact of thermoregulation on performance. The article critiques traditional measures of temperature regulation, such as variance of Tb and regression slope, which are insufficient to fully capture the complexity of thermoregulation. It proposes a new protocol that uses Tb, Te, and Tset data to provide a comprehensive, quantitative portrait of thermoregulation. The protocol is demonstrated using data from three Anolis lizard species in Puerto Rico, showing its utility and superiority to previous methods. The study emphasizes that temperature regulation is a complex process involving behavioral and physiological adjustments. It also discusses the importance of considering the thermal environment and the physiological state of the animals. The article concludes that the new protocol provides a more accurate and comprehensive understanding of thermoregulation in ectotherms, and that it can be applied to other organisms. The study also highlights the importance of considering the physiological impact of temperature regulation on performance, and how this can be measured using thermal sensitivity data.The article presents a new research protocol for evaluating temperature regulation in small field-active ectotherms, particularly lizards. It highlights the importance of understanding how accurately and effectively ectotherms regulate their body temperatures. The protocol requires data on body temperatures (Tb), available operative temperatures (Te), and the thermoregulatory set-point range (Tset). These data are used to estimate three quantitative indexes: the precision of body temperature (variance in Tb), the accuracy of body temperature relative to the set-point range (average difference between Tb and Tset), and the effectiveness of thermoregulation (how close Tb is to Tset compared to Te). The study also discusses how additional data on the thermal dependence of performance can be used to estimate the impact of thermoregulation on performance. The article critiques traditional measures of temperature regulation, such as variance of Tb and regression slope, which are insufficient to fully capture the complexity of thermoregulation. It proposes a new protocol that uses Tb, Te, and Tset data to provide a comprehensive, quantitative portrait of thermoregulation. The protocol is demonstrated using data from three Anolis lizard species in Puerto Rico, showing its utility and superiority to previous methods. The study emphasizes that temperature regulation is a complex process involving behavioral and physiological adjustments. It also discusses the importance of considering the thermal environment and the physiological state of the animals. The article concludes that the new protocol provides a more accurate and comprehensive understanding of thermoregulation in ectotherms, and that it can be applied to other organisms. The study also highlights the importance of considering the physiological impact of temperature regulation on performance, and how this can be measured using thermal sensitivity data.