The present paper deals with a critical appreciation of the role of the behavioural scientist in analysing organisational problems. A three-step model is elaborately discussed. It includes diagnosis, prescription and action. The various types of data gathering devices, types of data etc are included under diagnosis. Under the second step, different methods of bringing about desired change are outlined. Action stage includes the various strategies and possible pitfalls which one may face while implementing change. The paper is meant to provide a general frame for application of behavioural sciences know-how to organisational problems.