Anatomical investigation has been made on the stem of pigeonpea (Cajanas cajan (L.) Millsp.) at different stages of growth following the standard paraffin method of microtechnique. The vascular bundle of the stem are collateral and arranged in a ring. The cambium initiates in the primary vascular bundle between xylem and phloem at the basal part of the stem of 3 days old plant. After the formation of fascicular cambium it gives rise to secondary xylem adaxially and secondary phloem abaxially. Most of the vessel members are solitary and few are paired while others are multiple. The solitary vessel members are more in mature stem as compared to that of the younger stem. The well developed periderm was found in mature stem. The pith resembles a typical dicotyledonous stem.