We report two reading experiments and two questionnaire studies designed to investigate the processing of ''sluiced" sentences, like Somebody left- guess who. A self-paced reading experiment showed that sentences with explicit (overt) antecedents are read more quickly than sentences with implicit (covert) antecedents, both when the antecedents in question were arguments and when they were adjuncts. An eye movement experiment showed that sluiced sentences containing two potential antecedents were read faster than sentences containing only a single antecedent in matrix subject position. We suggest this is because only the ambiguous sentences contained an antecedent in a normal focus position (embedded object position). Two questionnaire studies suggested that perceivers prefer a focused constituent as the antecedent of the sluiced constituent. Since we argue that the interpretation of a sluiced constituent take place at the representational level of ''logical form" (LF), we conclude that implicit arguments are not made explicit at LF but that focus is important in the processing of LF.