An interferon inducer, based on the stabilization of poly I-poly C against nucleolytic destruction, has been produced. It has been shown to be a good interferon inducer, and an effective antiviral agent in non human primates against a number of serious virus diseases prophylactically and therapeutically. In man, it induces significant levels of interferon. In open trials in man strongly suggestive evidence of antiviral action has been seen. Double blind trials are underway.