Introduction: Triheptanoin provides long-chain fatty acid oxidation disorder (LC-FAOD) patients with an alternative to medium-even-chain triglycerides therapy. Material-methods: Retrospective analysis of 18 French LC-FAOD patients benefiting from early access to triheptanoin treatment. Results: Eight female and 10 male patients with LC-FAOD (VLCAD, LCHAD, CACT, CPTII and MTP) were treated with triheptanoin for a median duration of 22 months (range: 9-228 months). At last consultation, triheptanoin accounted for 15-35% of their daily caloric intake. In the year following the introduction of triheptanoin, patients reported a reduction of intermittent snacking and nocturnal meals. Three patients, including 1 adult, became free of severe hypoglycaemic events. Ten of 12 paediatric patients and 4 of 6 adult patients reported reduced fatigue with reductions in the number and severity of episodes of myalgia. Of 6 patients, including 1 adult, that had required the use of a wheelchair in the year prior to triheptanoin, all but one no longer required its use. The number of emergency hospitalizations decreased, and none were recorded for paediatric patients during these 12 months. Cumulative annual days of emergency care in the home were reduced from 286 to 51 days in the year before and after initiation, respectively, and 13 patients required no such interventions. Adverse events were limited to digestive issues that dissipated over time. Conclusions: Our case-series suggests that long-term treatment of LC-FAOD paediatric and adult patients with triheptanoin is safe and leads to marked improvement of symptoms and an improved quality of life.