Epilepsy is a common condition in people with learning disabilities with many patients continuing to suffer from seizures despite antiepileptic drug (AED) treatment. Although the advent of newer AEDs offers hope for better treatment, there is a need to compare the efficacy of each new AED in adults with both drug-resistant epilepsy and learning disabilities. This retrospective casenote study involves the analysis of the outcome for those adults with learning disabilities treated with either vigabatrin, lamotrigine or gabapentin. The information obtained from the casenote analysis was used to both compare the efficacies of the three drugs and also the side-effects and drop-out rates, including reasons for drop-out. The total number of patients involved was 51 who underwent 71 treatment episodes. All three AEDs had similar efficacies. Although vigabatrin was found to be associated with a higher incidence of behaviour problems, behaviour problems occurred with the other drugs as well. Lamotrigine caused increased seizures in 24% of patients, especially when prescribed at a higher dose. Gabapentin appeared to be associated with fewer serious side-effects.