Based on the analysis of thousands of conodont specimens from the Permian -Triassic (P-T) transition at Meishan (the GSSP of P-T Boundary) and Shangsi sections in South China, this study investigates the size variation of Hindeodus and Isarcicella P1 elements during the mass extinction interval. The results demonstrate that Hindeodus-Isarcicella underwent 4 episodes of distinct size reduction during the P-T transition at the Meishan Section and 2 episodes of size reduction in the earliest Triassic at Shangsi. The size reductions at Meishan took place at the junctions of beds 24d/24e, 25/26, 27b/27c and 28/29, and at the junctions of beds 28/29c and 30d/31a at Shangsi. The two earliest Triassic size reduction episodes were correlative between the two sections. These changes coincide with some important geological events such as eustatic sea-level changes, anoxic events, carbon isotope oscillations, miniaturization of brachiopods and microbial changes. Through detailed investigation of the palaeoenvironment and the palaeoecology of Hindeodus-Isarcicella, the authors propose that the main causes of the size reduction was a sharp decline of food availability because of the mass extinction and the anoxic event during the P/T transition. The pattern of size reduction supports suggestions that the end-Permian mass extinction was multi-episodal, consisting of 3 extinction events rather than a single catastrophic event. © 2008 Elsevier B.V. All rights reserved.