Protein-calorie malnutrition is frequently diagnosed in patients with serious digestive conditions displaying obstructive symptoms, notably in esophageal cancer. In the present study a homogeneous group of subjects affected by esophageal cancer and candidates for elective surgery was randomly treated by one of the following oral supplements: arginine (group I), glutamine (group II), or mixed commercial amino acids (Group III-controls). The methods included nutritional measurements (biochemical and anthropometric assement), immunologic survey (skin tests), and general clinical and surgical findings, with emphasis on surgical morbidity. Body weight remained stable throughout the study, whereas serum albumin, total lymphocytes and skin tests tended to improve in all groups, with statistical confirmation for albumin in arginine-treated cases (group II). Post-operative hospitalization was numerically shorter during glutamine supplementation, and this trend was statistically significant when total morbidity was compared between the groups. It is concluded that: 1) Malnutrition and anergy were a major problem in this population, with equally severe post-operative morbidity; 2) Administration of arginine enabled serum albumin levels to improve; 3) Glutamine-treated subjects displayed reduced post-operative morbidity; 4) No side effects could be attributed to the therapy here employed.