Someof the most remarkaLle rocks, especially in texture and genesis, are undou- btedlv the komatiites, which together with komatiitics basalts and/or tholeiites constitute the komatiitic suites. However. there are differences in geochemistry between komatiites from different areas and/or ages, providing a direct evidence of the physical and chemical changes of the mantle.Nesbitt and Sun (1979) recognized two kinds of komatiites: aluminum-undepleted komatiites (Group I) and alnum-depleted komatiites(Group II)discriminated by the hediagrams of Al2O23 vs. TiO2 and CaO vs.Al2O3.The typical examples are from Abitibi, Canada and Barberton. South Africa, respectively. Recently,Ohtani et al. (1989) identified a new kind of komatiites: alumium-enriched komatiites (Group III).The authhor documents that the Group III komatiites not only exist, but also have high Al2O3/TiO2 ratios caused by depletion of Ti instead of enrichment of alnminum. Although most of komatiites or komatiitic suites are of Archean ages and occur in greenstone belts, some also occur in Phanerozoic ophiolitic suites, such as the Cape Smith belt (Early Proterozoic)，Canada; Betts Cove (Ordovician)，Newfoundland, Canada; Othris Mountains (Triassic)，Greece and Gorgona Island (Tertiary)，Columbia. So far, the relationships between the various kinds of komatiites, komatiitic hasalts and tholeiites and their evolution throughout the geological time are not well-known, although that might be a key problem in the understanding of Archean and Phanerozoic crust-mantle evolution，This paper attempts to discuss these problems on the basis of the petroehemistry of over 500 samples selected from a database established by the author.