Methionine metabolism is altered in cancer, and methionine labeled with 11C has been successfully used for imaging of brain, lung, and breast cancer and lymphoma. Uptake of L-[methyl-11C]methionine (11C-methionine) in head and neck cancer of 23 patients was studied with PET. Accumulation of 11C-methionine in the tumors was assessed by two different methods: the influx constant, Ki, and the standardized uptake value (SUV). All 23 cancers accumulated 11C-methionine. The mean Ki was 0.147 +/- 0.070 min-1 and the mean SUV 8.5 +/- 3.5. There was a strong correlation between the two measures of tumor uptake (r = 0.92, p less than 0.0001). There was no correlation between the uptake of 11C-methionine and the histological grade of cancer. Head and neck cancer can thus be effectively imaged with 11C-methionine. Carbon-11-methionine PET imaging may be useful in delineating tumors for therapy planning.