Malnutrition, present in 16-50% of ALS patients, is an independent prognostic factor for worsened survival. It is caused primarily by swallowing dysfunction, resulting from involvement of the lower sets of cranial nerves, but hypermetabolism is also implicated. Malnutrition itself can produce neuromuscular weakness and adversely affect patients' quality of life, thereby creating a vicious circle. The nutritional status of ALS patients can be assessed with dietary review and measurements of weight (W) and height (H). A body mass index (BMI = W/H2) below 18.5-20 kg/m2 indicates a state of malnutrition. Dietary counselling is important, but rapidly becomes insufficient, particularly in bulbar-onset ALS, where enteral nutritional support is then necessary. Percutaneous endoscopic gastrostomy tube placement is well tolerated, and provides more efficient enteral nutrition than nasogastric tube feeding. Enteral nutrition support can improve the respiratory status of ALS patients. The effect on survival remains to be confirmed.