Tissue expression and stock variation of isozymes of stone flounder (Kareius bicoloratus) were analyzed with horizontal starch gel electrophoresis. For the fourteen enzymes assayed, 31 loci were recorded. The results indicated that all the isozymes examined were obviously tissue-specific. The expressions of SOD*, GDH*, G3PDH-2* and ADH-2* were detected only in liver, SDH-1*, MDH-1* and ADH-1* only in muscle, and LDH-B* and LDH-C* only in eyes. In comparison, MDH-2*, GPI-3* and SDH-2* were detected in all tissues examined. Other loci examined were detected in a variety of tissues. Muscle and liver were selected to detect the isozyme variation of the two geographic stocks of Qingdao and Weihai, Shandong Province, China. The percentages of polymorphic loci (P0.99) were 29.17％ and 25.00％, the observed heterozygosities (H0) were 0.028 ±0.014 and 0.040 ± 0.019, and the expected heterozygosities (He) were 0.039±0.017 and 0.052±0.022 in Qingdao and Wethai stock, respectively. The coefficient of gene differentiation (Fst) and genetic distance (D) between the two stocks was 0.012 and 0.0011, respectively, indicating that the genetic differentiation is low between them. Compared with other species of Pleuronectiformes, both the percentage of polymorphic loci and the mean heterozygosity ofK. Bicoloratus were at a middle level.