This paper examines the efficiency in the stock markets of India, Sri Lanka, Pakistan and Bangladesh. The Augmented Dickey Fuller (ADF-1979, 1981), the Phillips-Perron (PP-1988), the Dicky-Fuller Generalized Least Square (DF-GLS-1996) and Elliot-Rothenberg-Stock (ERS – 1996) tests are used to examine weak form stock market efficiency. Weak form efficiency is supported by the classical unit root tests. However, it is not strongly supported for Bangladesh under the DF-GLS and ERS tests. Cointegration and Granger causality tests are used to examine semi-strong form efficiency. Semi-strong form efficiency is not supported as these tests indicate a high degree of interdependence among the South Asian stock markets. The above results have implications for domestic as well as foreign investors in South Asian stock markets.