OBJECTIVES To determine the role of type 1 cytokines as predictors of response to treatment of genital HPV lesions with laser ablation with or without adjuvant systemic interferon alpha 2b (IFN-alpha). METHODS Measurement of serum interleukin 2 (IL-2), IL-2 soluble receptor alpha (sIL-2 alpha), interferon gamma, and human papilloma virus (HPV) DNA in patients undergoing treatment of genital HPV lesions with carbon dioxide laser and systemic IFN-alpha. A randomised, placebo controlled study of 92 cases with 6 months of follow up. RESULTS High IL-2/sIL-2 alpha was associated with 60% to 70% protection against recurrences both in the IFN-alpha and placebo groups (OR = 0.4, 90%, CI 0.1-2.5; OR = 0.3, 90% CI 0.0-1.8, respectively). Diagnostic phase serum IL-2 predicted favourable outcome (OR = 0.2, 90% CI 0.0-1.0) in women with high load of HPV DNA or HPV 16/18 DNA regardless of the adjuvant therapy. CONCLUSIONS Serum IL-2 determinations may identify women with good prognosis following laser ablation of genital HPV lesions.