We investigated the incidence of the following conditions: inflammatory neurological and neuromuscular diseases, adult meningitis and adult encephalitis in Yonago City, and Guillain-Barré syndrome (GBS), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), polymyositis/dermatomyositis (PM/DM), periarteritis nodosa (PN) and HTLV-1 associated myelopathy (HAM) during the period 1988-1992 in Tottori Prefecture, Japan. The annual incidence per 100,000 population was as follows: meningitis, 4.38; encephalitis, 0.90; GBS, 1.14; PM/DM, 1.01; and PN, 0.32. The prevalence per 100,000 population CIDP, 0.81; PM/DM, 9.92; PN, 2.59; and HAM, 1.30. There were marked localization of HAM in western Tottori, and there was seasonal variation in the prevalence of meningitis, encephalitis and GBS. The mean age at onset of meningitis was lower than that for encephalitis. Comparison with reported data revealed interracial differences in the epidemiology of PM/DM and PN.