Temporal numerosity discrimination was investigated for visual, auditory and tactile senses. Trains of two to nine signals (flashes, clicks, taps) were presented at rates of from 3 per sec. to 8 per se. The subjects were instructed specifically to report only the number of signals counted. Significant modality differences were obtained. Auditory counts were almost perfectly accurate inder all conditions. Visual judgement of number, which were consistently the least accurate, were underestimated. The error increased appreciably as the rate increased from 3 per sec. to 6 per sec. but decreased with rates of 7 per sec. and 8 per sec. Tactile reports also underestimated the actual number of signals, the underestimation increasing linearly as a function of rate.