This is the first of three volumes dealing with clausal architecture, grammatical relations, case-marking and the syntax-semantics interface in Baltic. It focuses on the grammatical relations of subject and object and the viability of these notions in languages like Lithuanian and Latvian, which have a rich case morphology and show many deviations from the canonical nominative-accusative pattern of case-marking. The issues examined include differential object marking, subjecthood in specificational copular constructions, `swarm'-type alternations and what they tell us about grammatical relations, special types of subject and object marking in non-finite clauses, and non-canonical grammatical relations induced by modal predicates. One study provides a comparative outlook towards Icelandic, another language noted for its complex marking of grammatical relations. The articles in the volume represent various theoretical frameworks.