OBJECTIVE: The authors report their experience in patients with adjuvant systemic 2-interferon with the aim of defining the effectiveness, side-effects, indications and limitations of this treatment. MATERIALS AND METHODS: From January 1989 to December 1996, 123 patients with genital, anorectal and perineal HPV lesions were treated with cryosurgery; adjuvant systemic a2-interferon was administered to 38 of them. There were 76 female and 47 male patients (median age of 29 years, range; 15-56 years). Clinical examinations included: digital rectal examination, head and neck examination, urethral meatus inspection and, in female patients, gynaecological examination; they underwent colposcopylurethroscopy, proctosigmoidoscopy, cystoscopy (in advanced disease); scraping for cytology and PCR analysis, and biopsy for histology. Twenty-three percent of patients had more than one site involved; upper digestive tract involvement was observed in 6.6% and 47% had lesions larger than 6 sqcm. Twenty-five females with genital lesions had esocervical lesions only; ten of them had SIL1, while seven a SIL3. RESULTS: Ninety-eight out of 123 patients (79.7%) were recurrence-free after a median follow-up of 32 months. A recurrence was observed in 25 patients: in univariate analysis, recurrence of disease occurred more frequently in females (p = 0.04), in patients with longer duration of symptoms (p = 0.0002),with wider lesions (p = 0.00015), with head and neck involvement (p < 0.01), and in HIV-positive patients (p = 0.03). In multivariate analysis, duration of symptoms (p = 0.005), head and neck involvement (p = 0.01), and width of lesion > 3 sq cm (p = 0.025) were associated with increased risk CONCLUSION: Our findings confirm the value of cryosurgery in the treatment HPV lesions; it is less traumatic, and gives good aesthetic and functional results; moreover, large lesions may be treated and the depth of cryonecrosis is more suitably adapted. Patients amenable to adjuvant treatment with a2-interferon should have multiorgan involvement, HPV type 16 or 18, lesions >3 sqcm, long lasting symptoms (>6 months) and presence of SIL.