This study focuses primarily on the inflection of singular place-names belonging to strong declensions and how their inflection developed in the Old Swedish period. It is based mainly on sources from Södermanland.

Examination of the dative inflections of masculine and neuter place-names suggests that by and large place-names underwent the same course of development as appellatives, the dative having almost completely disappeared as a formal category by the end of the Middle Ages. In some cases dative endings were, however, retained in place-names: for example, certain name elements tended to keep the ending when they occurred as simplexes, but lost it in compound names. The dative may then have become the general form of such names.

A special study was made of iō-stem place-names. Even in the nominative, forms ending in -e and -a predominate. The -e ending derives from the dative/accusative form, which may have become a new basic form at an early date. Reinterpretation of the dative/accusative resulted in someplace-names passing into the weak declension. Via the dative/accusative singular ending, place-names also adopted the generalized -a form which developed in plural habitative names.

In the Middle Ages a mode of inflection peculiar to place-names appeared. In Latin texts, Swedish place-names occur in a generalized form, used regardless of case. A suitable form was chosen, often an accusative which had converged with the nominative. Generalized forms of this kind are found in both Latin and Old Swedish texts. The Latin scribal tradition was a contributory factor in their introduction.

The author discusses whether place-names can be shown to have changed paradigm earlier than appellatives. Secondary -s genitives in particular, which occur earlier in place-names than in appellatives, suggest that they did. The fact that place-names exhibit secondary -s genitives in early sources may be partly due to their naming function.