Our objective was to assess the effects of acetyl-L-carnitine (ALC) with riluzole on disability and mortality of amyotrophic lateral sclerosis (ALS). Definite/probable ALS patients, 40-70 years of age, duration 6-24 months, self-sufficient (i.e. able to swallow, cut food/handle utensils, and walk), and with forced vital capacity (FVC) > 80% entered a pilot double-blind, placebo-controlled, parallel group trial and were followed for 48 weeks. ALC or placebo 3 g/day was added to riluzole 100 mg/day. Primary endpoint: number of patients no longer self-sufficient. Secondary endpoints: changes in ALSFRS-R, MRC, FVC and McGill Quality of Life (QoL) scores. Analysis was made in the intention-to-treat (ITT) and per-protocol (PP) population, completers and completers/compliers (i.e. taking > 75% of study drug). Forty-two patients received ALC and 40 placebo. In the ITT population, 34 (80.9%) patients receiving ALC and 39 (97.5%) receiving placebo became non-self-sufficient (p = 0.0296). In the PP analysis, percentages were 84.4 and 100.0% (p = 0.0538), respectively. Mean ALSFRS-R scores at 48 weeks were 33.6 (SD 10.4) and 27.6 (9.9) (p = 0.0388), respectively, and mean FVC scores 90.3 (32.6) and 58.6 (31.2) (p = 0.0158), respectively. Median survival was 45 months (ALC) and 22 months (placebo) (p = 0.0176). MRC, QoL and adverse events were similar. In conclusion, ALC may be effective, well-tolerated and safe in ALS. A pivotal phase III trial is needed.