Analyses of karyotype of cells obtained from amniotic fluid were made for the past ten years with the purpose of improvement of the culture condition and better clinical application. Direct inoculation of unspan specimens of more than 19 weeks and less than 2 days old gave better results and harvest by mechanical detachment of cells without trypsin gave better metaphase spreads for the analysis. Repeated amniocentesis was necessary in 28% of the cases with higher rate for those specimens of 18 weeks or less and 3 days old or more. About thirteen per cent of the cases had their first amniocentesis after 22 weeks gestation. Twenty-five per cent of the cases received amniocentesis were of advanced maternal age. An additional 50% had Down's syndrome in the previous birth. The highest incidence and variety of chromosome aberrations were found in advanced maternal age group. Two incorrect diagnoses were found only in sex identification and prenatal diagnosis was concluded highly reliable.