The study explores the psycholinguistic processes underlying L2 self-repair behavior by means of analyzing the timing of various types of self-corrections found in the speech of 30 Hungarian speakers of English at three levels of proficiency (pre-intermediate, upper-intermediate, and advanced). The paper discusses the relevance of timing data for the existing models of speech monitoring and examines how the level of proficiency of L2 learners affects the speed of error detection and the execution of correction. The results obtained indicate that the perceptual loop theory and the activation spreading theory of monitoring both rightly assume that monitoring involves the same mechanisms as speech comprehension. The analysis of the timing data reveals that corrections of pragmatically inappropriate lexical choice have detection times very similar to those of lexical errors. This may be regarded as indirect evidence for the claim that lexical entries in the mental lexicon also contain specifications concerning their pragmatic value. The results show that the level of proficiency of the participants affects the time necessary for the lexical, grammatical, and phonological encoding of the repair, which is caused by the difference in the degree of automaticity of these mechanisms at various stages of L2 development.