Seventy commercial apple juice concentrates were analysed to determine the correlation between patulin and fumaric acid content. No significant correlation was found for the samples having patulin lower than 50 mu g/L. The samples containing patulin levels ranging from 67 to 216 mu g/L had a slightly higher correlation coefficient of 0.55. The most significant correlation coefficient of 0.71 was determined when all 70 samples were taken into account. Two different varieties of apple having different initial patulin and fumaric acid content (47 +/- 2 mu g/L patulin/2.75 +/- 0.13 mg/L fumaric acid and 299 +/- 16 mu g/L, patulin/3.68 +/- 0.31 mg/L fumaric acid) were processed into apple juice concentrate to determine the effects of different treatments on patulin and fumaric acid. As expected, both patulin and fumaric acid content decreased through all the processing steps except evaporation An appreciable amount of fumaric acid formed during evaporation while no remarkable change was observed in patulin.