PURPOSE: Our purpose was to examine the timing of implantation and early embryo development following uterine transfer of oocytes/embryos previously subjected to zona pellucida micromanipulation. METHODS: A total of 68 singleton pregnancies resulting from IVF and embryo transfer with/without micromanipulation. Patients were divided into four groups according to the type of micromanipulation technique: assisted hatching, embryo biopsy, intracytoplasmic sperm injection, and no micromanipulation (control group). Serial serum beta-hCG levels were measured between 10 and 25 days after fertilization and log-transformed. Linear regression analyses were performed and extrapolated to hCG = 10 mIU/ml (hCG10) to estimate detectable implantation. The slopes of the regression lines were used to estimate the rising speed of hCG, an indirect sign of embryo development. RESULTS: There were no significant differences among groups with respect to hCG10, the slopes or intercepts of the regression lines. CONCLUSIONS: Various oocyte/embryo microsurgical procedures used in ART involving zona pellucida manipulation do not appear to affect the timing of implantation or early embryo development.