Validation is an integral part of text comprehension. We used reading times and plausibility judgments to investigate combined effects of source credibility and plausibility on validation. Participants read stories with a high- vs. –low-credible person making knowledge-consistent, implausible, or knowledge-inconsistent assertions. Interactions of source credibility and plausibility were found for plausibility judgments and reading times, indicating that source credibility affects validation but that the pattern of effects depends on the degree of implausibility.