Synchronization for a pair of chaotic oscillators is studied both numerically and experimentally. The two oscillators are Coupled unidirectionally, namely, in the master slave configuration. When the coupling strength is systematically varied, different regimes of chaotic synchronization such as no, phase, lag and complete are identified. The existence of natural lag synchronization for unidirectional coupling is by virtue of a small parameter mismatch between the master and the slave oscillators. Numerical calculations are carried out in the Rossler model whereas the experiments are performed using a pair of electrochemical oscillators.