The contamination of foreign particles in the injection solution at ampouleopening process using scissors and injectors was investigated with the commercial plastic ampoules.After opening the ampoules by the each method, foreign particles present in the injection solution were collected on the membrane filter of 0.45μ pore size and observed by optical and electron microscopes. It was shown by analysis of fluolescence-X ray, furthermore, that these were small pieces of plastc. From measuring the distribution of these particle size by Luzex 450 Particle Analyzer, it was indicated that 5-25μ of particle size was most and the average number was not significant between the two opening methods.The injection solutions were also contamined by micro-organisms at the opening process. This contamination could be prevented by disinfection or sterilization of the ampoules and the instruments used.