Evolutionary study of a rotating 20M. star with a chemical composition appropriate for the Large Magellanic Cloud (LMC) has been carried out starting from the threshold of stability through the gravitational contraction phase, approach to the main-sequence, on the hydrogen burning phase, upto the point at which 61% of hydrogen was consumed in the central region of the star. During evolution mixing due to diffusion has been taken into account. As a consequence of such a mixing it has been shown that the atmosphere of the star was enriched the most conspicuously in helium and nitrogen. Thus it was concluded that rotational mixing helps the star to expose processed matter at its surface. When compared with the observations of nitrogen rich early type stars, our results agree well with the observed chemical composition of the OBN stars, if not quantitatively but at least qualitatively.