Background:Leishmania parasites are transmitted to humans and mammals by sandfly vectors in the form of flagellated promastigotes that propagate inside tissue macrophages in the form of aflagellateamastigotes. Majority ofinformationon sequential development is derived from that of the kinetoplastids:trypanosomatidae; notably that of T. brucei. Objective:Investigationof ultra-morphologic events involved in Leishmaniareplication to provide a detailed description of the sequential processes by which Leishmaniareplicates its single-copy organelles. Material and Methods:Leishmaniapromastigotes weremaintained by invitro culture,and amastigotes were attained by inoculation of laboratory out bred male Syrian hamsters with cultured promastigotes.Concentrated pellets of promastigotes and 1mm thick tissue biopsies from infected hamsters were optimally processed for electron microscopy. Ultrathin-sections were examined and photographed bya Zeiss EM 952 electron microscope. Results:In promastigotes and amastigotes,initial amplification of subpellicular microtubules resulted in morphometric increase in size of the dividing forms.Replication of nucleus and kinetoplast was asynchronous. Kinetoplast S phase occurred before commencement of nuclear S phase.Lengthening and merging of the kinetoplastmitochondrion occurred into that of the amastigote cellandcoincided with detection of the hidden basal body which started duplication of the flagellum.Separation of basal body, flagellar pocket and flagellum appeared to occur before kinetoplast division which was found to divide and separate before closed mitosis (pleuromitosis).Centrosomes were recognized in the centre of the spindle synchronously with the K-DNA lengthening. Cytokinesis progressed from the posterior pole to the anterior pole of the cell along the longitudinal axis, bisecting the cell symmetrically. Conclusion:Compiled records provided definite information on the sequential cellular cycle of the Leishmaniaspp. and the chronological proceedings of replication of their nucleus and kinetoplast. Replicationbynuclear (karyokinesis)and cytoplasmic (cytokinesis)division machineries, documents its non-conformability with its taxonomicallyrelatedtrypanosomatids