A preliminary study of event related potentials (P300) in a group of 16 cancer patients, without cerebral metastases or focal neurological deficits, is being reported. As compared to a group of 28 normal adults, 9 out of 16 cancer patients were found to have prolonged P300 latencies, and 6 made more than two errors in their cognitive performance. These subclinical cognitive impairments in cancer patients may be related to some remote effects of cancer. These patients had not undergone any chemotherapy or radiation therapy prior to P300 studies. Further studies in a larger group of patients with gynecological cancer are being conducted.