To assess possible solvent-induced dysfunction of the autonomic and peripheral nervous systems, 11 solvent-exposed workers and 11 age-matched unexposed controls were examined using the coefficient of variation in electrocardiographic R-R intervals (CVRR) and the distribution of nerve conduction velocities (DCV). Two components of CVRR, i.e., the C-CVRSA and C-CVMWSA, were also examined, which are considered to reflect parasympathetic and sympathetic activities, respectively. The workers had been occupationally exposed to toluene and/or solvent mixtures such as thinners, for 35-360 months. In the solvent-exposed workers, the CVRR and C-CVRSA were significantly reduced compared with unexposed controls. Similarly, the faster velocities of the DCV and median nerve conduction velocities were significantly slowed. The reduction in the CVRR was significantly correlated with duration of exposure in the solvent-exposed workers. These data, despite the small sample size and the variety of organic solvents, suggest that organic solvents may affect both the faster myelinated nerve fibers and autonomic nervous activity (principally, parasympathetic component).