The central nervous system can be described in terms of its ability to detect and categorize various spatiotemporal patterns in the sensory receptor arrays and to produce coordinated behavior by providing appropriate control signals to the individual effectors. This task is achieved by a vast network of neurons, and, therefore, it may be difficult to fully understand the functional significance of the activity of individual neurons outside the context of the network. Direct information concerning the role of individual neurons in a network can be obtained by simultaneously recording the activity of several neurons. For that purpose, we have been using a seven-electrode system to examine neuronal activity in the primate cortex while the animal performs various behavioral tasks. This chapter first describes our recording system and software/hardware for spike isolation and then reports some results from our analysis on the activity of neurons recorded simultaneously during a simple visuomotor task. Specifically, we sought to evaluate ensemble measures computed post hoc from a number of trials by comparing them to the same measures computed from a single trial. We were interested in the neuronal population vector (Georgopoulos et al., 1983), which is a measure of the directional tendency in a neuoronal ensemble.