The disabling, dialysis-responsive symptoms of clinical uremia primarily represent impaired functions of the nervous system. Accordingly, these studies used several quantitative electrophysiologic and cognition-dependent probes of nervous system function: peripheral nerve-conduction velocity, response latency and amplitude; electroencephalographic (EEG) power-spectrum analysis; visual evoked response latency; EEG responses to photic driving; and measures of integrated behavioral performance that stressed sustained and selective attention, reaction time, speed of decision-making, short-term memory, and mental manipulation of symbols. Probes of quanitified central nervous system function consistently revealed impairments that varied directly with the degree of renal failure, that improved following onset of maintenance dialysis, and that improved still further after successful renal transplantation. In contrast, measures of peripheral nerve function were generally unchanged. Neurobehavioral measures that are relevant to uremic symptomatology provide quantitative estimates of the clinically significant, whole-organism biologic effects of renal failure and its several treatments. Applications of such measures in studies of symptomatic states other than uremia are indicated also.