Background & method: Degree and the nature of crystallinity determines several key properties of a polymeric system. Thermal analysis, although widely used for crystallinity determination, has limited precision with oriented polymeric devices, due to the differential nature of multiple thermal events (cold-crystallisation, chain-relaxation, etc). We have for the first time studied, how MDSC (Modulated DSC) variables manipulate the thermal behaviour of oriented materials, so that the degree and the nature of crystallisation can be well defined. 27 combinations using following values of variable were studied- Period (ρ) = 60, 80, 100 seconds; Amplitude (α) = 0.1, 1, 2; Heating rate (τ) = 2, 5, 100C/ min. Oriented polylactic acid films were used as a model system. Results were validated by comparison to 2D-WAXD. Results: MDSC curves suggested that the thermal events were significantly shaped by α and ρ. A dual crystallisation peak was observed for higher α. While, the area of the peak representing crystallisation into a less stable form increased as the ρ decreased. Estimated crystallinity decreased inversely with the heating rate, and α due to time dependent crystallisation and melting. This effect was consistent in MDSC for 'heat-only' cycles. Heat-cool-heat cycles lead to crystallisation of some part of the polymer in a less stable crystal form, whose melting was visible as a non-reversible event. The observations suggested that the heat-only cycles with low amplitudes, higher period and faster heating rates favour accurate estimation of the crystallinity, whereas heat-cool-heat cycles with higher amplitude help in understanding pre-melting thermal events associated with polymer orientation or the crystal perfection. Results were consistent with WAXD data. Conclusion: An optimised MDSC can be used as a rapid and accurate method for estimation of the crystallinity as well as assisting in understanding the nature of crystallisation in an oriented polymeric system.