The normal range of eye-hand span was defined for a three-choice serial task, and attempts were made to increase and reduce the span in related tasks, in order to discover the factors determining its limits. The normal span was shortest at fast display speeds. An attempt to reduce it to .30 sec. was unsuccessful; it simply produced an increase in errors and omissions. However, a comparable method gave a mean response time of only .14 sec. in tracking a slow harmonic course. The normal span was longest at slow display speeds. It could be increased temporarily by speed stress, although never as far as twice the interval between displays during accurate serial performance. When the span was increased beyond this point by instructions, errors increased, especially with faster speeds of performance. It was concluded that the amount of information required in order to respond was a determinant of the lower limit of the span. The amount of information to be held in store, and the rate of storing and reproducing information, were both determinants of the upper limit.