GABA plays a vital role in many functions and present in 6-70% of all synapses within CNS. GABA binds to three major receptor types: GABA-A, GABA-B, and GABA-C. GABA-A receptors are primarily ligand gated Chloride channels receptors. Unlike Benzodiazepines, Tiagabine does not act directly or indirectly on GABA receptors. It selectively inhibit Gat-1 transporter of GABA, Tiagabine is the only available GABA Reuptake inhibitor clinically available. This is a prospective open study of a randomly selected group of children and adolescents with Pervasive Developmental Disorder. This is an open label study, suffers from all shortcomings of studies of that type. The sample size may also be a small one. Other problems like selection bias should also be considered before any conclusion is made. These defects, however, do not take away its value as a pioneer project that indicates a possible value in treatment of one of the refractory disorders in childhood and adolescence. Tiagabine is seemingly useful as an adjunct drug. It is approved as such in treatment of seizure disorders, and it was used in this study in an augmenting strategy to treat refractory anxiety complicated by aggressive behavior and stereotypic movement disorder. A positive study of this type should call for more definitive work like a double blind placebo controlled studies.