The concept of unreliable narration is intimately linked with the concept of fictional truth. The question what is true in the fictional world of a narrative fiction is in itself one of the most intriguing problems of literary studies, but the difficulties related to answering the question become even more severe when dealing with unreliable narration. The article addresses the inference of fictional truth in unreliable narrations (part 2) against the background of what it generally means to explore fictional worlds and to infer fictional truth (part 1). The discussions are based on an institutional theory of fictionality and draw upon various attempts to adapt possible-worlds theory to literary studies. Part 1 focuses on the critical discussion of the concepts of fictional truth and fictional worlds, especially in relation to the so called Reality Principle and Mutual Believe Principle. It is argued that inferring what is fictionally true in a work, i. e. making assumptions about the existing states of affairs of a fictional world, is based on a complex set of operations, and that the way they are used may differ to a certain extent from text to text and from interpretation frame to interpretation frame. Principles like the Reality Principle or the Mutual Believe Principle may have their share in these inferences, but only in a way that takes into account much more complex and broad considerations about norms of rationality in interpretation. Part 2 addresses specific difficulties concerning the inference of fictional truth in narrations that may be considered as unreliable. It is argued that unreliable narration in fictional texts can be described as the counterpart of the fact that in actual-world communication the Gricean Cooperative Principle can be violated. It is argued that interpretations of a fictional narration as unreliable based on this assumption can to a certain extent be described as being in accordance with the Reality Principle. Furthermore, the paper explores how specific insight about interpretive operations in connection with unreliable narration and fictional truth may be gained on the ground of Marie-Laure Ryan's adaptation of possible-worlds theory to literary studies. The explorations specifically draw upon Ryan's distinction between the textual actual world (TAW) and narrational actual world (NAW) and Ryan's elaboration of what she calls the domain of a character in a narration. This domain is divided in different worlds: the epistemic or knowledge world (K-world) for what a character knows, the wish world (W-world) for the wishes, needs and drives of a character, defined by axiological predicates, and the obligation world (O-world) defined by the social rules and moral principles of the group the character belongs to and by his own moral judgements. The different categories that Ryan proposes are understood as interpretational devices. When we deal with fictional narrations what we take as TAW, NAW or private character-worlds are always the result of our interpretative operations on the text. Bearing this in mind, Ryan's distinction between the different private worlds of a character and a close observation of the relationships of these worlds with NAW and TAW can help us to gain insights into what it means to interpret a fictional narrative as unreliable. We can ask e. g. how, to what extend and why a reader may construe NAW as different from TAW, and how, to what extend and why assumptions about character-worlds come into play Moreover, these questions help to reconsider the discussion about the relevance of the distinction between homodiegetic and heterodiegetic narration in regard to unreliable narration. Finally, a distinction can be made between temporary and persistent unreliability.