Precocious puberty is one of the major constraints to the further development of Chinese mitten crab (Eriocheir sinensis) farming industry. Although dietary phospholipids (PL) and highly unsaturated fatty acids (HUFA) supplementation have been shown to enhance the growth of larval E. sinensis in other studies, it is still unknown whether this also leads to a higher precocity rate for juvenile E. sinensis. This study was conducted to investigate the e¡ects of dietary PL and HUFA on precocity, survival, growth and hepatic lipid composition of juvenile E. sinensis. Two diets were formulated with PL [3.95% dry weight (DW)] and HUFA (0.98% DW) supplementation (diet A) and without PL and HUFA supplementation (diet B) and fed to juvenile E. sinensis. Although dietary PL and HUFA levels did not signi¢cantly a¡ect the survival and growth performance of juvenile E. sinensis, compared with crabs fed diet A, a higher precocity rate was found among juvenile E. sinensis fed diet B (P 5 0.051). A higher total lipid content, but sig-ni¢cantly lower levels of HUFA and PL (Po0.05) were found in the hepatopancreas of crabs fed diet B than in those fed diet A. Meanwhile, the precocious females had signi¢cantly lower hepatosomatic index , arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) contents in their hepatopancreas when compared with that of the normal immature juveniles (Po0.05). The results suggest that the occurrence of precocious puberty among farmed juvenile E. sinensis could be reduced by the inclusion of appropriate level of dietary PL and HUFA. Ã Vitamin mix: 1kg of diet contained vitamin A 10 000 IU; vitamin D 2500 IU; vitamin K 64 mg; thiamin 60 mg; ribo£avin 250 mg; pyridoxine 60 mg; a-tocopherol acetate 500 mg; L-ascorbic acid 4.5 g; calcium panthothenic 240 mg; niacin 60 mg; folic acid 12 mg; biotin 50 mg; cyanocobalamine 4 mg. wMineral mix: 1kg of diet contained Ca(H 2 PO 4 ) 2 10 g; MgSO 4 Á 7H 2 O 2.4 g; KCl 4.5 g; NaCl 2.1g; FeSO 4 Á H 2 O 155 mg; CuSO 4 Á 5H 2 O 40 mg; ZnSO 4 Á H 2 O 80 mg; MnSO 4 Á H 2 O 30 mg; KI 11.7 mg; CoCl 2 Á 6H 2 O 4.8 mg; Na 2 SeO 3 2.4 mg. Bold highlights the level di¡erence between two diets. Aquaculture Research, 2011, 42, 457^468 Dietary PL and HUFA on the precocity of juvenile Eriocheir sinensis X Wu et al. r