As an experimental model for the research of open neural tube defect (NTD), the surgical model has several advantages over others, in spite of the fact that the pathogenetic mechanism is not compatible with the human intrauterine events. To make reproducible NTDs by surgery and to compare the surgically induced lesions with the human myeloschisis morphologically, we opened the neural tube for a length of 9-11 somites in Hamburger and Hamilton stage 16-19 chick embryos. Embryos which survived until the late in ovo life (total age 14 and 21 days) showed relatively reproducible open NTDs. Morphologically they are similar to human myeloschisis. This study suggests that the surgical model can be suitable for studies of open NTDs.