A retrospective audit of the perceived efficacy and tolerability of adjunctive gabapentin (GBT) therapy in patients with intractable epilepsy was carried out. The case-notes of 263 consecutive patients attending a tertiary referral centre in whom GBT had been added to concomitant anti-epileptic drugs were reviewed. There were 119 males (45%); the median age was 35 years (range 15-81 years) and the median duration of epilepsy was 20 years. The median dose of GBT administered was 1,600 mg (range 300-4,800 mg). Twenty-nine patients (11%) had a reduction in seizure frequency of greater than 50% and 7 (3%) achieved seizure freedom of 6 months' duration at least while taking GBT. Side-effects were reported by 169 patients (61%) and in 40 (15%) an increase in seizure frequency of 50% occurred, this being the commonest reason for GBT withdrawal. The median duration of treatment was 4 months (range 0.03-47 months). Ten patients, in whom GBT therapy had proven ineffective in doses of 900-1,800 mg, were rechallenged with doses of 300-4,800 mg. One individual experienced a 50% reduction in seizure frequency and 1 an increase in seizures of at least 50%. GBT was generally well tolerated at high doses and rechallenge of a small number with GBT in doses up to 4,800 mg did not result in further improvement in seizure frequency in the majority.