A deflectable biopsy catheter for obtaining a tissue sample from a body cavity of a patient comprising: an axially elongated catheter shaft having proximal and distal portions respectively terminating at proximal and distal ends, the catheter shaft being sized and constructed to be advanced into a body cavity of a patient; a deflection wire coupled to the distal portion of the catheter shaft and extending within the catheter to the proximal end thereof; and a pair of biopsy jaws coupled to the distal end of the catheter shaft and having first and second opposed free cutting surfaces exposable for contact with a selected area of tissue within the patient's body cavity and movable with respect to each other to cut a tissue sample from the selected area of tissue. Schemes for obtaining samples from body cavities (e.g., the gastrointestinal tract, the heart, the intestines, the uterus, the muscles, the bile duct, and the esophagus) are disclosed. Schemes for treating tissue by ablation or by electro-coagulation are also disclosed.