Modifications to the 4-aminoantipyrine-potassium ferricyanide procedure for the colorimetric determination of phenols have lead to the development of 3 micro-methods. These were introduced to reduce the sample volume while maintaining the reproducibility of the assay. For that purpose, we have also investigated the possibility of combining some of the reagents. When applied to the evaluation of the arylesterase-like activity of albumin on α-naphtyl acetate via the dosage of α-naphtol, we found an excellent inter-assay reproducibility without compromising our initial goals of accelerating the procedure and reducing the sample volume.