This chapter focuses on the peri-operative monitoring of the heart, circulation, respiratory system and brain function in the morbid obesity (MO) surgical patient. Intra-arterial blood pressure (BP) monitoring is the gold standard, but is not necessary in the otherwise healthy MO patient undergoing a simple surgical procedure. Transcutaneous oxygen tension monitoring has been used for many years in neonatal critical care as a surrogate for arterial oxygen tension. Body temperature should be measured in patients undergoing general or neuraxial anesthesia procedures exceeding 30 min duration. Neuromuscular activity should be monitored during surgery by train-of-four (TOF). Electroencephalogram (EEG)-based brain function monitors have been introduced to optimize the dose of anesthetic agents by monitoring electrical equivalents of levels of awareness. The decision to use bispectral index (BIS) monitoring in MO patients undergoing general anesthesia, and especially total intravenous anesthesia, is still a matter of choice.