Analysis of skin-test results obtained with compound 48/80 [p-methoxyphenethyl methylamine formaldehyde product] indicated that this substance deserves a place in the standard series of test fluids for routine skin testing. No influence of sex or season was detected, but there were significant differences in response related to the age (strongest reactions in the 16-40 yr age group) and to the diagnosis (strongest reactions in the atopic patients).