The objective of this work was to study the effect of SO2 and ascorbic acid on polyphenol oxidase (PPO) and peroxidase (PO) activities in some fruits and vegetables. For the fruits and vegetables PO, ascorbic acid was considered the best method of inactivat ion. On the other hand, for the fruits and vegetables PPO, SO2 was the most effective method, but did not control PO activi ty in almost all products studied. A combination of the two componds used (SO2 and ascorbic acid) seems to be the adequate method to control simultaneously both enzyme activities.