Objective. To study the incidence of asthenopia among computer terminal operators as compared to unexposed administrative workers and to identify the risk factors associated with this condition. Material and methods. A sample of 35 computer terminal operators and 70 unexposed administrative workers from eight computing centers at an educational institution were included in the study. The risk factors studied were: lighting, contrast, type of lighting, screen type, electrostatic field, eye to monitor distance, time and number of hours worked, age, use of corrective lenses, seniority and overtime. Asthenopia was clinically identified as the presence of at least one sign and symptom present in a given workday. Results. Asthenopia was found in 68.5% of the exposed group and in 47.7% of the unexposed group (p menor que 0.05). Among the risk factors studied, working for more than four hours at the video display terminal was shown to have a significant association with asthenopia (p menor que 0.05). Conclusions. A recommedation is made to take breaks during the workday at computer terminals in order to avoid visual fatigue. Also, more extensive studies should be carried out in our population to establish safety criteria and to standardize work activities using computer terminals.