Thirty-five patients had prick skin tests to the common allergens Candida albicans. Aspergillus fumigatus, grass pollen, horse dander and Dermatophagoides pteronyssinus performed on a regular basis from Autumn 1973 to Autumn 1975. Specific IgE to the same allergens (except C. albicans) was determined at the time of skin testing for the first five seasons. It was found that the position on the volar aspect of the forearm on which the test was performed did not affect the reaction. There was a significant variation in the percentage of patients with positive skin tests to A. fumigatus, grass pollen and horse dander with the latter showing as significant decrease with time. There was evidence of variation in weal size for all but C. albicans, and for grass pollen, horse dander and D. pteronyssinus there were reduction in weal size with time. Significant differences were found for results of Log specific IgE for grass pollen and D. pteronyssinus over the study, but there was no trend. A good correlation between weal size and Log specific IgE for grass pollens and D. pteronyssinus was observed. For the four allergens, the coefficient of concordance between IgE levels within patients for the five seasons was highly significant.