A duel fuel diesel engine is a diesel engine fitted with a dual fuel conversion kit to enable use of clean burning alternative fuel like compressed natural gas. Dual fuel engines have number of potential advantages like fuel flexibility, lower emissions, higher compression ratio, better efficiency and easy conversion of existing diesel engines without major hardware modifications. In view of energy depletion and environmental pollution, dual fuel technology has caught attention of researchers as a viable technology keeping in mind the increased availability of fuels like Compresed Natural Gas (CNG). It is an ecological friendly technology due to lower PM and smoke emissions and retains the efficiency of diesel combustion. Traditionally dual fuel technology has been popular for large engines like marine, locomotive and stationery engines. However its use for automotive engines has been limited in the past due to constraints of limited supply of alternative fuels. This paper highlights the methodology and outcomes of the recent experimental and simulation research work carried out for development of dual fuel diesel CNG engine for heavy duty application. The paper also throws light on present limitations and drawbacks of dual fuel engines and proposed methods to overcome these drawbacks. A parametric study of different engine operating variables affecting performance of diesel-CNG dual fuel engines vis-à-vis base diesel operation is also summarized for a six cylinder heavy duty engine. Chemical kinetic and Computational Fluid Dyanamics (CFD) simulation of dual fuel diesel-CNG engine combustion has also been carried out. Development challenges and future development trends for these engines is also discussed in detail.