OBJECTIVE To examine advance care planning and outcomes of patients with amyotrophic lateral sclerosis (ALS) receiving long-term mechanical ventilation (LTMV). METHODS Case series. METHODS Population-based study in homes and chronic care facilities in four states, and Home Ventilator Program of California Kaiser Permanente. METHODS Seventy-five ALS patients receiving LTMV were identified; 11 died prior to interview, and 6 were totally locked in; 50 of 58 (86%) who were able to communicate consented to structured interviews, of whom 36 lived at home and 14 in an institution. RESULTS Thirty-eight patients (76%) had completed advance directives, and 96% wanted them. Thirty-eight patients wished to stop LTMV in certain circumstances, of whom 30 had completed advance directives. Those who had completed advance directives were more likely to have communicated their preference, to stop LTMV to family and physician than those who had not (76 vs 29%; p = 0.05). Patients living at home rated their quality of life on a 10-point scale better than those in an institution (7.2 vs 5.6; p = 0.0052), and their yearly expenses were less ($136,560 vs $366,852; p = 0.0018). CONCLUSIONS Most ALS patients receiving LTMV would want to stop it under certain circumstances, and the process of advance care planning enhances communication of patient preferences to family and physicians. Home-based LTMV is less costly and associated with greater patient satisfaction.