Pityriasis versicolor is a superficial fungal infection of the skin. It is caused by Malassezia. This fungus is part of the normal skin flora but may cause illness when it transforms to its harmful hyphal form. The actual pathophysiology of pityriasis versicolor has not been understood. In recent decades, it has been claimed that overproduction of reactive oxygen metabolites and/or inadequate production of antioxidants may drive cell death. Oxidative stress driven buildup of harmful free radicals may have a pathophysiological effect in the development and progression of PV. Production of reactive oxygen species (ROS) may lead to a shift in the cellular redox state. The purpose of this research was to evaluate the probable involvement of oxidative stress in the pathogenesis of pityriasis versicolor, by evaluating blood levels of malondialdehyde (MDA) and total antioxidant capacity (TAC) in active pityriasis versicolor patients. Methods: This research comprised 60 pityriasis versicolor patients and 30 healthy controls. All patients were exposed to thorough history, full general and dermatological examination. This research was done at Dermatology, Venereology and Andrology Outpatient clinic of Benha University Hospital from April 2019 to December 2019. Results: Serum MDA level was considerably raised (2.56±1.53) nmol/ml in patients compared to controls (1,38±0.46) nmol/ml, (p value> 0.001). Serum TAC level indicated no statistically significant difference between patients and controls. Using ROC analysis, at the cut off point of MDA>1.9 n mol/ ml, the sensitivity of MDA was 63.33 percent , The specificity of MDA was 93.33 percent , positive predictive value in MDA was 95 percent , and negative predictive value in MDA 56 percent . Using ROC analysis, There was a sensitivity of 60%, specificity of 96%, a 97% positive predictive value, a 54% negative predictive value, and a cutoff of 0.5 mM/L for the TAC test. For both MDA and TAC, there were no statistically significant relationships with age or BMI. No correlations were found between serum TAC levels and several clinical factors (sex, smoking, recurrence, family history and site). Different clinical factors did not seen to have a statistically significant correlation with the blood level of MDA (sex, smoking, recurrence, family history and site). It is clear from this study that MDA has a role in the aetiology of pityriasis versicolor, since the serum MDA level was considerably higher in patients compared to controls. Oxidative stress may have a role in the aetiopathogenesis of pityriasis versicolor, as shown by the presence of MDA.