A randomized trial comparing routine follow-up with a treatment regimen aimed at increasing specific anti-tumour immunity has been carried out in 95 patients after total surgical excision of lung cancer (not small-cell). Treatment consisted of inoculation with an autologous irradiated suspension of tumour cells combined with a small dose of C. parvum given intradermally during convalescence. Although treatment was associated with virtually no side effects, there has been no apparent benefit and input to the trial has now stopped.