Background/Purpose: A report in the literature suggests longer duration and greater intensity of late phase UVB erythema in older people. The aim of this study was to identify differences in minimum erythema dose (MED) and intensity of UV-induced erythema after narrow band UVB exposure between older and younger individuals in the late phase of UVB erythema. Methods: Using the UVA/TL 01 UV skin tester (Waldmann Medizintechnik, Villingen-Schwenningen, Germany), MED was determined for narrow-band UVB exposure in 20 young subjects aging from 20–40, and 20 elderly subjects over 70 years of age. The intensity of UV-induced erythema was measured by chromametry (a*-value and L-value) and laser Doppler 48 h after irradiation. Minimum erythema dose (MED) was additionally assessed visually. Results: Elderly subjects showed no statistical different MED compared to younger subjects. However, the erythema intensity 48 h after narrow-band UVB exposure was significantly greater in the elderly. Conclusions: Narrow-band UVB therapy may, in case of over dosage, produce more intense erythema in the late phase of UVB erythema in old people than in younger individuals.