['To compare the chromosome error rate among oocytes from stimulated ovaries after retrieval of 1-5 oocytes, 6-10 oocytes, and >10 oocytes.', 'Retrospective cohort study.', 'A university-based human genetic institute in collaboration with a private fertility center.', 'Nine hundred thirty-three women undergoing intracytoplasmic sperm injection (ICSI) with a poor prognosis.', 'Oocyte collection with ovarian stimulation. Polar body testing of ICSI oocytes for common chromosome errors.', 'Chromosome error rate in oocytes, as determined by five-color fluorescence in situ hybridization.', 'In women less than 35 years and women between 35 and 40 years undergoing the first ICSI cycle, oocytes from the high-yield group had an increased likelihood for detectable chromosome errors (50.9% and 54.6%, respectively), compared to the intermediate-yield group (34.9% and 43.8%) and the low-yield group (23.3% and 41.2%). The overall high rate (>or=50%) of chromosomally abnormal oocytes in women more than 40 years appeared to be mainly due to the maternal age effect and increased only slightly with oocyte yield.'] Is a high oocyte yield for intracytoplasmic sperm injection treatment associated with an increased chromosome error rate?