A key event in the domestication and breeding of the oil palm Elaeis guineensis was loss of the thick coconut-like shell surrounding the kernel. Modern E. guineensis has three fruit forms, dura (thick-shelled), pisifera (shell-less) and tenera (thin-shelled), a hybrid between dura and pisifera1, 2, 3, 4. The pisifera palm is usually female-sterile. The tenerapalm yields far more oil than dura, and is the basis for commercial palm oil production in all of southeast Asia5. Here we describe the mapping and identification of the SHELLgene responsible for the different fruit forms.