Beagle dogs between 7.6 and 8.8 years of age administered a twice daily supplement of -lipoic acid (LA) and acetyl-L-carnitine (ALC) over 2 months made significantly fewer errors in reaching the learning criterion on two landmark discrimination tasks compared to controls administered a methylcellulose placebo. Testing started after a 5 day washin. The dogs were also tested on a variable delay version of a previously acquired spatial memory task; results were not significant. The improved performance on the landmark task of dogs supplemented with LA + ALC provides evidence of the effectiveness of this supplement in improving discrimination and allocentric spatial learning. We suggest that long-term maintenance on LA and ALC may be effective in attenuating age-associated cognitive decline by slowing the rate of mitochondrial decay and cellular aging.--Milgram, N. W., Araujo, J. A., Hagen, T. M., Treadwell, B. V., Ames, B. N. Acetyl-L-carnitine and -lipoic acid supplementation of aged beagle dogs improves learning in two landmark discrimination tests.