Immune system amplification by perilesional injection of interleukin-2 is a promising adjuvant approach for treating squamous cell carcinoma of the head and neck. A pilot study was designed to develop an animal model bearing squamous cell carcinoma in which to test the efficacy of perilesional interleukin-2. Rabbits were inoculated intramuscularly with the papilloma virus - induced squamous carcinoma VX-2 cell line. Tumor regression and host lymphatic response after perilesional interleukin-2 were measured. Variable responses were found. Growth of tumor cells implanted from cell culture was rapid in most animals. Tumor growth was prevented in animals receiving 10,000 units of interleukin-2 per injection initiated 9 days after tumor inoculation. This inhibition approached statistical significance when compared with growth of saline controls. Histologic responses consisted primarily of plasma cell and eosinophil infiltration. The intensity of the inflammatory response did not correlate with interleukin-2 dose. A trend toward enhanced tumor growth was seen with lower doses of interleukin-2 and when interleukin-2 therapy was initiated simultaneously with tumor inoculation. These findings suggest that high-dose recombinant interleukin-2 can prevent tumor growth if initiated after tumor inoculation. Whether this effect was caused by direct tumor cytotoxicity or mediated by the immune system is unclear. These preliminary results underscore the importance of understanding the effects of dose and schedule in the design of immunotherapy models before clinical use. (OTOLARYNGOL HEAD NECK SURG 1995;112:430-6.). © 1995.