Purpose: Glass particle contamination of the contents of single-dose glass ampules can occur upon opening. Different aspiration techniques, different sizes of needles, different sizes of ampules, and different cutting methods were studied to determine if they had any effect on glass particle contamination. Method: Different aspiration techniques(with filter, without filter), different sizes of needles(18G, 25G), different sizes of ampules(2ml, 20m1), and different cutting methods(with cotton, without cotton) were evaluated. Method: Twenty ampules were randomly assigned in each group. Three slides containing glass particles for each ampule were made and counted under a microscope by 3 study blind persons. Result: The number of glass particle contamination is much less when using a filter rather than without a filter. The number of glass particle contamination is much less when using a 25G needle rather than on 18G needle. The number of glass particle contamination is much less when using 2ml ampules rather than 20m1 ampules. The number of glass particle contamination is much less when using cotton rather than without cotton. Conclusion: It was shown that using a filter, a small size needle, smaller sized ampules and using cotton when cutting the ampule will decrease the risk of parenteral injection of glass particles.