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INRIA-Rocquencourt, BP 105, 78153 Le Chesnay Cedex, France We propose a modest onservative extension to ML that allows semiexpli it rstlass polymorphism while preserving the essential properties of type inferen e. In our proposal, the introdu tion of polymorphi types is fully expli it, that is, both introdu tion points and exa t polymorphi types are to be spe i ed. However, the elimination of polymorphi types is semiimpli it: only elimination points are to be spe i ed as polymorphi types themselves are inferred. This extension is parti ularly useful in Obje tive ML where polymorphism repla es subtyping. 1999 A ademi Press