Theoretical Foundations: A General Equilibrium Approach.- The Harris-Todaro Migration Model and Introduction of the Informal Sector.- Informal Sector and Open Unemployment.- Foreign Capital Inflow, Informal Sector and Welfare.- How and How Far to Liberalise a Developing Economy.- Economic Liberalisation, Informal Wage and Skilled-Unskilled Wage Inequality.- Incidence of Child Labour, Informal Sector and Economic Liberalisation.- Informal Sector, Pollution and Waste Management.- Conclusion and Comments.