Drawing from the fields of physics, biology, medicine, physiology, and fitness sciences, we have developed a physics laboratory activity that introduces RC electric cir- cuits in conjunction with Bioelectric Impedance Analysis (BIA). Designed to demonstrate the electrical properties of the human body as relevant to medical science, the activity involves students in the dual analysis of both physical and bi- ological systems. The concepts of impedance and frequency dependence are explained using RC circuits and a cellular- level analysis of body tissue. Experiments are performed on both of these systems using an educational BIA device we custom designed for this activity. In the BIA laboratory described here, students acquaint themselves with the concepts of resistance, capacitance, im- pedance, and phase shifts in ac circuits. Circuits are con- structed to emulate the bioelectrical behavior of the body, and an educational BIA device is used for measurements. Students are invited to make measurements on their own bodies using the same device. The data are compared with empirical fits for impedance and body composition, which students use to calculate their own body fat percentage and fat-free mass. These estimates are compared with measure- ments taken by a commercially available BIA device. Single- and multiple-frequency analyses are performed, exposing students to different circuit models of the body in an active exploration of ac circuitry. Finally, student atti- tudes were surveyed before and after the laboratory and the results are discussed in the final section of this paper.