Polyphenoloxidase (PPO) is responsible for browning of damaged fruits and vegetables by catalysing hydroxylation of monophenols to o-diphenols and oxidation of o-diphenols to o-quinones in the presence of oxygen. These reactions decrease fruit quality, since PPO has been regarded to be a critical enzyme in food technology. Cashew culture has a large socioeconomic importance to Brazilian Northeast because of commercial products of nut and pseudo fruit. However, the fruit is highly perishable, requiring especial care during storage, transportation, cleaning and processing. The purpose of this work was to study the effects of substrate concentration, different pHs and presence of sodium dodecyl sulfate (SDS) on PPO activity from cashew apple. To prepare the crude extract, 100 mL of cashew apple juice, obtained by using a juice extractor, was added to 200 mL of 0.01 M phosphate buffer (pH 6.5) and centrifugated at 11000 rpm for 30 min at 4 ºC. The supernatant was brought to 70% (NH₄)₂SO₄ saturation and the precipitate, which had activity, was separated by centrifugation at 11000 rpm for 30 min at 4 ºC. The precipitated fraction was redissolved in phosphate buffer and dialysed overnight against the same buffer. The dialysed extract was used as the PPO source in the experiments. Enzyme activity was determined with catechol as synthetic substrate by measuring the increase in absorbance at 420 nm. The sample cuvette contained 450 mL of the enzyme solution, 450 mL of phosphate buffer (pH 6.5) and 100 mL of catechol in concentrations ranging from 0.005 to 1 M. To determine optimum pH, a mixture of 0.1 M buffers (citrate, tris, glicine and sodium acetate) was used. The effect of SDS was studied adding a solution 1.5 mM of SDS, 30 min before measuring PPO activity. PPO activity increased for all catechol concentrations analyzed. At highest concentration, enzyme activity did not show steady-state after 240 min of reaction. Maximum activity was obtained at pH 6.5. The presence of SDS had no effect in enzyme activity showing that PPO from cashew apple is present in its active form.