Conjugated dienes content is one of the factors for determining the quality of gasoline. Owing to their easy polymerization, the presence of these compounds decreases the quality of the product. Although UOP-326, the traditional method for their determination, is still in use, it has some disadvantages such as: long analysis time, incomplete reaction with some conjugated dienes, and the interference of primary alcohols. The main objective of this work is to propose a faster and more reliable method, using the voltammetric technique, for the determination of conjugated dienes value in Brazilian naphtha samples. The results point out some advantages of the proposed method, such as: less analysis time, better recovery, a good selectivity, the non-interference of alcohols, and the possibility of direct analysis of commercial gasoline. (c) 2006 Elsevier Ltd. All rights reserved.