This study examines the duration modulation of C1VC2V- sequences in Korean. We conducted two production experiments to test the effect of nonlocal stops on durations of segments. In Experiment 1, Seoul and Gwangju Korean speakers recorded C1aC1ata and C1alata (C1 = lenis, aspirated, and tense stops) sequences. The results showed that C1VOT of aspirated stops was significantly shorter before another aspirated stop, as in Mongolian (Svantesson and Karlsson 2012), but that neither F0 nor H2-H1 were affected. The follow-up experiment, in which the types of stimuli were increased, provided two more findings. First, the trigger of shortening is ‘long VOT’ rather than the laryngeal feature [asp]. As well as the C1 aspirated stop, the C1 lenis stop shortened the VOT of the C2 aspirated stop. Second, the shortening effect is bidirectional. Not only C2 long VOT shortened C1 VOT, but also C1 long VOT shortened C2 VOT. This cannot be accounted for by segmental OCP or gradient dissimilation because the effect is purely phonetic, and the two stops do not become more different. We argue that the data is explained by an isochrony tendency which modulates long periods of segments. In addition, we adopted a V-to-V interval to account for the duration modulation beyond syllables.