This non-random, convenient, open study was designed to observe the efficacy of lamotrigine as monotherapy in Bipolar II Disorder. 71 patients (42 males & 29 females) were enrolled from an out patient psychiatric facility in Lahore, Pakistan. The used diagnostic criterion was DSM-IV. Severity of Mania and depression was checked by Young’s Mania Rating Scale (YMRS) and Hamilton Depression Rating Scale (HDRS) respectively. Patients were selected with poor response to lithium either alone or in combination with valporate or carbamazepine. Lamotrigene was given to them for two years and they were assessed at months 0, 1, 2, 4, 8, 12, 16, 20 and 24. The dose of Lamotrigene used was 100-200 mg/day as a single dose. 57 (38 males & 19 females) patients completed the study period while remaining. 14 (4 males & 10 females) were drop out possibly due to poor response or deviation from the protocol. After two years 57 patients who completed the study period, Lamotrigene was found effective in 70% (28 males & 12 females). In addition it was also found well tolerated in majority of the patients.