Criteria- based international classificatory systems like the ICD and DSM have ensured greater reliability for the diagnosis of schizophrenia. These, however, are an index of reliability, rather than validity. There is an accumulating evidence for shared genetic/ environmental risk factors and neurobiological abnormalities between schizophrenia and bipolar disorder. Much of the evidence accumulated over the past twenty years points to a significant overlap and commonality of genetic heritage between schizophrenia and bipolar disorder. This article attempts to present an overview of the problems in delineating schizophrenia from bipolar affective disorder and suggest some alternatives Key words: Schizophrenia, Diagnosis, International classification of diseases (ICD), Diagnostic and statistical manual (DSM).