Erythromycin is known to have both antibiotic and anti-inflammatory activity. It has been used to treat guttate psoriasis. A double-blind, placebo controlled trial was performed using 34 patients with guttate psoriasis at the Out Patient Department of the Philippine General Hospital. Each patient received either placebo or erythromycin stearate 1g in divided doses for 14 days. The response was graded according to the percentage change in Psoriasis Activity and Severity Index (PASI) score after 2 weeks. The results reveal similar baseline demographic characteristics between two treatment groups. After 2 weeks, the average PASI score change improved in the placebo group (9.1 to 8.5) and worsened in the treatment group (9.1 to 11.3). Using the two sample t-tests, there was no significant difference between the to treatment groups in terms of PASI score after 2 weeks. Thus, at present we cannot recommend antibiotic monotherapy in patients with guttate psoriasis.