The study hypothesis is that changes in serially obtained nerve conduction study data obtained every 3-4 weeks in cancer patients receiving chemotherapy can be used to predict the development of a clinically significant / disabling drug induced neuropathy six and twelve months following the start of treatment. Patients with breast cancer, colon cancer, gastroesophageal cancer, and non-Hodgkins lymphoma will be enrolled. Six lower extremity nerves--three in each leg--will be electrically stimulated and their responses recorded at three to four week intervals coinciding with patient's scheduled chemotherapy.