Information-transfer (IT) rates in bits/sec were estimated for a variety of methods of human communication and modalities of reception. Using previously published data, a range of communication rates for which transmission is highly accurate was established for each method and modality. These communication rates were converted into a normalized unit of transmission (words/sec). The normalized units were then converted into estimates of IT rate (bits/sec) using Shannon's (1951) calculations of the information content of a single letter of the alphabet. Maximal estimates of IT rates of roughly 40 to 60 bits/sec are observed for speech (through audition) and for reading and sign language (through vision). Maximal rates roughly 50 percent lower are obtained for reading through the tactual sense. Estimates of IT rates for motor output tasks are also considered. A close correspondence is generally observed between IT rates for receiving a given display and IT rates for the motor output task required for producing the display. These results have implications for the design of synthetic-environment systems and the displays and controls to be used in these systems, by providing examples of communication rates that have been achieved by humans in the area of language communication.