Purpose: the current study was to compare between the effect of polarized light therapy (PLT) and betamethasone phonophoresis in the Treatment of psoriasis. Subject: fifteen patients were included in this study. Their ages ranged from 25 to 60 years. Each patient was divided into two sides Procedures: Group (I) received polarized light therapy (PLT) with a specific energy den¬sity of 40 mW cm. The light is brought and applied to the required area at constant intensity and very low energy but it is constant at 2.4 joule cm2 per min. In addition to topical corticosteroids for 4 weeks, 3 days/week. Group (II) received 4 weeks of treatment with betamethasone diprobionate phonophoresis (BDP) using continuous mode for 5 min, with 1 MHz and 1.5 W/cm2, 3 days/ week while. Group (I) received 4 weeks of treatment with topical corticosteroids only while. The measurements were done before the study and after one month of treatment for all groups by using Ultrasonography. Results: of this study showed reduction in the thickness of skin after the treatment for Group (A), (B) and (c) with a percentage of 41.66%, 29.16%, and 8.69% respectively for the thickness of skin. There was a highly significant difference between groups after the treatment. It was observed that PLT was more effective than betamethasone diprobionate phonophoresis. Conclusion: It could be concluded that. Biptron light therapy (BLT) is more effective than betamethasone phonophoresis in treatment of psoriasis.