The deoxy analogues of D-glucose, 1-deoxy-D-glucosamine and D-glucosamine, are biochemically and structurally similar to 1-deoxy-D-glucose, so their direct effects on food intake were studied. Both 12 and 24 mumol 1-deoxy-glucosamine potently decreased feeding and body weight after an initial transient elicitation of food intake. The suppression included decreased meal size and prolonged postprandial intermeal interval which persisted for at least 3 days after injection. Ambulatory activity was unaffected. The initial elicitation of feeding was not accompanied by drinking episodes, and subsequent drinking suppression was persisted. These findings, plus other biochemical evidence, suggest that inversion with an amino group or removal of a hydroxyl group from C-2 and/or C-1 may affect feeding.