Background: Semantic network abnormalities in patients with psychotic disorder were examined using associative prime-target relations with two stimulus asynchronies (SOAs; -250 ms and -500 ms) to assess the time course of automatic and more controlled processes of semantic priming. To investigate whether an aberrant semantic network system is part of the familial liability for psychosis, healthy siblings of patients with psychotic disorder were additionally examined. The N400 event-related brain potential (ERP) was used as a probe of semantic processing. Method: Twenty-two patients with psychotic disorder, twenty siblings of patients with psychotic disorder and twenty controls participated in a lexical decision task and ERPs were recorded to target words that were associatively, indirectly or not related to their preceding prime word. Results: Associative priming of the N400 amplitude was found across all participants and both SOAs, but no between-group differences were found for the N400 amplitude (both SOAs). The Group × Condition interaction of the indirect priming N400 latency of the three groups was just short of statistical significance (F2,59 = 2.7, p = .077). Patients showed an increased indirect priming effect of the N400 latency only at short SOA, with decreased latency of the indirectly related compared to the unrelated condition, while controls did not show an indirect priming N400 latency effect. No between-group differences in N400 latency of indirect priming were found at the long SOA. Only a trend towards a Group × Condition interaction of the indirect priming N400 latency between the sibling and the controls was found, but without a main effect of indirect priming in the sibling group. Conclusion: These preliminary results support the assumption of a hyperactive semantic network in patients with psychotic disorder, which develops under automatic processes and decreases with more controlled processes, but does not represent clear trait familial liability. © 2012 Elsevier B.V.