The objectives of this study were to investigate the prevalence and risk factors of occupationally related carpal tunnel syndrome (CTS) among workers employed in services and manufacturing industries analysing the sensitivity and specificity of clinical symptoms and signs. Three surveys were made for this study. The first survey was done for 1,447 workers employed by 25 companies. The jobs of the employees were repetitive works at VDT and assembly lines. Therefore, employees could be divided to two groups, doing repetitive works and non repetitive works. The second survey was made for 189 workers who were randomly selected from 517 workers complained some symptoms at their hands and wrists. We examined their symptoms and carried out neurological examinations for CTS (Tinel's sign, Phalen's sign, pin prick test, carpal compressive test, toniquet compression test). The third survey was made for nerve conduction study (NCS) for 57 workers who had shown positive signs for CTS. The main results of this study were as follows: 1. From the first survey, we have found that there were significant statistical differences in getting uncomfortable neuromuscular symptoms by sex, job type, total working hours during a week, duration of current work, and kinds of work. Odds ratio in male vs female, repetitive vs non repetitive, service vs manufacturing companies, total working hours during a week, and duration of current work were 1.867(95% CI=1.467-2.377), 1.680 (95% CI=1.121-2.279), 1.663(95% CI=1.213-2.279), 1.016(95% CI=1.006-1.027) and 1.283 (95% CI=1.097-1.501) respectively. 2. From the second survey, we have found that 46 peoples (25.0%) were positive for one or more than one signs in neurological examinations of NIOSH criteria. Positive findings from neurological examinations were high among workers of low level of education (p-value=0.008), manufacturing jobs (p-value=0.00), long hours a week (p-value=0.028), and long duration of current work (p-value=0.00). 3. From the third survey, we diagnosed 35 peoples (61.4%) had CTS by NCS. They had abnormally delayed latent period or velocity in median nerve conduction velocity.