BACKGROUND: Routine methods of chromosome G-bending are complicated, time-consuming and worse in effect, which is not suitable for clinical examination and teaching investigation of chromosomal disorder.OBJECTIVE: To seek for proper method of improving the effect of chromosome G-banding.DESIGN: Observation experiment.SETTING: Xinxiang Medical University.MATERIALS: The experiment was conducted in the Laboratory of Morphous, Xinxiang Medical University between January 2001 and January 2005. 376 blood samples were obtained from patients with infertility and sterility or those had abnormal childbearing history, who came from the Clinic of Gynecology and Obstetrics, Third Hospital Affiliated to Xinxiang Medical College between 2001 and 2004. Main agents: RPMI1640 culture fluid (GIBCO Co., Ltd), 20% calf serum (CS), colchicines, 0.075 mol/L KCL, methanol, glacial acetic acid, trypase (SIGMA Co., Ltd) and Giemsa staining solution.METHODS: Modified method of human peripheral chromosomal preparation and G-banding: The procedures were the same as routine methods, while partial influential factors were regulated, for example, the action time of colchicines was set at 2 hours before the ending; 1 mL of fixation fluid (the ratio of methanol and glacial acetic acid was 2:1) was added for pre-fixation, and samples were mixed and centrifuged at 1 500 r/minute for 10 minutes. After re-centrifugalization,fresh fixation fluid was added to prepare for cell suspension and glass slide by according to the amount of cells.Above-mentioned glass samples were baked at 50 ℃ for 1-2 hours, naturally cooled to 37 ℃, digested for 3-5 minutes by immersing into trypase, rapidly stained for 10 minutes with Giemsa staining solution, and counted by the test under microscope to observe 3 000 metaphases, and the percentages; The percentage of 400-600 metaphases and well-dispersion rate were calculated. Well-dispersion rate of chromosome referred to the overlapping after dispersion with complete numbers. The trabant and kinetic body were obvious and in bright color with clear shape. Moreover, all chromosomes were on the same plane. The percentage of metaphase = the number of metaphase cells (400-600)/number of cells under observation×100%.MAIN OUTCOME MEASURES: The percentage of 400-600 pieces of metaphases in samples and good integration chromosome.RESULTS: 400-600 metaphases obtained with routine methods accounted for 52% with a well-dispersion rate of 68%,while 400-600 metaphases obtained with modified methods accounted for 75% with a well-dispersion rate of 86%, and there were significant differences between the two groups (P ＜ 0.05).the stripes are chear.CONCLUSION:Chromoseme metaphases obtained with modified methods are more in number and good in dispersion with proper size. Giemsa shows that the stripes art chear.