Two experiments were conducted to measure the oxygen uptake (Experiment II) and the carbon dioxide production (Experiment I) during transcendental meditation. A control group of non-meditators and a few meditators listening to music was used for both experiments. In Experiment I, a controlled group of fasting meditators was also included. A drop in oxygen consumption and carbon dioxide production, found by previous authors during transcendental meditation, was confirmed. It was, however, possible to show that these drops were physiologically of small significance, and were of the magnitude to be expected from muscle relaxation. EEG recordings were taken during Experiment II in the meditating group. The EEG results showed transcendental meditation to be a method of holding the mediator's level of consciousness at stage 'onset' sleep. No evidence could be found to suggest that meditation produced a hypometabolic state beyond that produced by muscle relaxation and there was no evidence that the EEG changes were different from those observed in stage 'onset' sleep. No support was found for the idea that transcendental meditation is a fourth stage of consciousness.