To investigate whether erythemal responses to ultraviolet radiation alter with age, we have reviewed the results of monochromator phototesting in adults and children, and have measured the dose–response curves for UVB erythema in a further 38 subjects. There was no significant difference between adults and children in minimal erythema dose (MED) at 300 nm; the median MED in 254 adults was 34 mJ/cm2 (range 14–80 mJ/cm2) and in 24 children aged less than 15 years was 30 mJ/cm2 (range 10–80 mJ/cm2). Objective measurements of UVB-induced erythema were performed in 15 subjects aged below 25 years and 23 subjects aged above 60 years. A dose–response curve for UVB erythema was constructed for each subject and the slope of the steepest part of each curve calculated by logit regression; the values in the young subjects were greater than in the older group (P<0.02). However, there was no difference between the two groups in either the visually assessed MED or the calculated UVB dose required to produce a constant degree of mild erythema.