This is an extension of an earlier paper (Sheridan, 1992) that considered alternative meanings and significance of “presence,” the experience of “being there,” commonly called “telepresence” in the case of remote control or teleoperation, and called “virtual presence” in the case of computer-generated simulation. In both cases presence can include feedback to the human senses of vision, hearing, and haptics, both kinesthetic and cutaneous. Presence is discussed here in terms of alternative subjective meanings, operational measurements, and meaningful experimental comparisons. Three practical approaches to measurement of presence are compared, including elicitation of “natural” neuromuscular or vocal responses, single or multidimensional subjective scaling, and ability to discriminate the real and immediate environment from that which is recorded/transmitted or synthesized. A new proposal, fitting into the third category, is to measure presence according to the amount of noise required to degrade the real and virtual stimulation until the perceived environments are indiscriminable. The author also opines on the stimulus magnitude, space, and time attributes of human interactions with a tele- or virtual environment.