Our objective was to investigate the nutritional requirements in ALS and to determine the feasibility of early intervention with NIPPV. Subjects were enrolled into one of two arms. In the nutrition arm, total daily energy expenditure (TDEE) was determined longitudinally over 48 weeks using the Doubly Labeled Water method. In the NIPPV arm, NIPPV was offered at 80% vs. 50% FVC. Additional measurements were obtained in both arms to ultimately formulate equations to predict TDEE and to estimate sample size for a phase III study of early NIPPV. Eighty subjects were enrolled in the nutrition arm and 73 in the NIPPV arm. Baseline characteristics of the participants are described. TDEE was available for 80 subjects in 249 independent determinations during disease progression. Other variables were measured simultaneously for future modeling of ALS-specific equations to predict TDEE. In the NIPPV arm, rates of progression to the criteria for NIPPV intervention (80% or 50% predicted FVC) were computed. Additional factors were obtained longitudinally to develop indices of early ventilatory insufficiency. The results of this study will allow us to model equations to predict the energy requirements in ALS and to plan a study of early intervention with NIPPV.