Hourly mean values of incoming UV-B irradiance measured by UV-B Photometer at Visakhapatnam (17.70°N, 83.30°E) were analyzed and the variability of incoming UV-B irradiance with solar zenith angle and total column ozone is investigated in terms of RAF (Radiation Amplification Factor) for three wavelengths 310, 290 and 280 nm. A regression model for estimating UV-B irradiance from TOMS ozone, air-mass, sun-earth distance correction and solar zenith angle was developed for this station. With the developed model long-term variation of incoming UV-B irradiance for the period 1978 - 1993 was evaluated using TOMS ozone. A study was carried out on the possible effect of UV-B irradiance on human beings (erythema) in terms of RAF and solar zenith angle which indicated higher erythemal sensitivity at lower solar zenith angles.