This chapter explores Lakatos’s modification of the Popperian position on the demarcation between science and pseudoscience, with the shift of the unit of appraisal from the theory to the research programme and the addition of criteria of theoretical and empirical progress. The structure of a Lakatosian research programme is described. The way in which this obviates some of the problems raised by epistemological holism, while at the same time maintaining criteria of demarcation, is examined. There are then discussions of Marxism and neoclassical economics as examples of research programmes which have been accused of being regressive and degenerating, and therefore pseudoscientific in Lakatosian terms.