Drosophila neuroblasts are an ideal model for studying asymmetric cell division, in which cell polarity is coupled to mitosis. Atypical protein kinase C (aPKC), which forms a complex with Bazooka and Par-6, is essential for establishing neuroblast polarity and for proper asymmetric cell division. Previous work has shown that, upon entry into mitosis, phosphorylation of Par-6 by Aurora-A kinase prevents a Par-6–aPKC interaction, thereby activating aPKC. Although the tumour suppressor Lgl is known to inhibit aPKC at the substrate level, the putative dephosphorylation event that negatively regulates aPKC activity in this pathway was unknown. On p. 3242, Fumio Matsuzaki and colleagues now provide new evidence on how aPKC activity is balanced to maintain polarity in neuroblasts. Using a genetic screen, the authors show that Mts – the catalytic subunit of protein phosphatase 2A (PP2A) – is an antagonist of aPKC signalling, and that cell division of Mts-deficient neuroblasts is defective. Biochemical evidence shows that Mts physically interacts with and directly dephosphorylates Par-6, permitting Par-6 to inhibit aPKC activity. The authors conclude that PP2A, together with Lgl, antagonises the positive action of Aurora-A kinase on aPKC in neuroblasts, thereby modulating the balance of aPKC activity required for asymmetric cell division.