Scalar additive operators such as Engl. even, Fr. même, Germ. sogar and Sp. aun vary cross-linguistically in terms of their distributional properties, in particular with respect to polarity (positive vs. negative, upward entailing vs. downward entailing). Such distributional differences can be regarded as reflecting variation in the lexical content of the relevant expressions themselves, rather than just combinatorial properties or differences in scope relationships. In this talk we proposes a typology of scalar additive operators that distinguishes five basic types. On the basis of a sample of 40 languages, the distribution of these types in European languages is surveyed, and the typology is shown to allow for some generalizations concerning both the distributional behaviour of specific scalar additive operators, and the make-up of entire systems of such operators. The "lexicalist" approach to the interpretation of scalar operators taken in this study is carried further by relating the lexical meanings assigned to the various operators to their historical sources. It is assumed that restrictions on (systems of) scalar additive operators can ultimately be derived from possible and impossible historical developments in the domain of investigation.