The effect of particulate matter and stability of three parenteral drugs upon addition to glass and flexible polyvinyl chloride containers of 0.9% sodium chloride injection was studied. Aminophylline, lidocaine hydrochloric and metaraminol bitartrate were added to the solution in therapeutic quantities using techniques normally practiced by the hospital pharmacist. Statistical comparisons of the amount of particulate matter present were made for each solution consisting of drug added to plastic and glass bottles, drug filtered through a 0.22-mum filter and then added to the solution in plastic bags, controls for bags and bottles, and solutions with adjusted pH values to simulate the pH attained after addition of the drug to the solution. A correlation appeared to exist between the quantity of particulate matter and the amount of unfiltered drug solution added to the large-volume parenteral containers. Differences in storage and handling had an influence on the initial quantity of particles found in the plastic bags, no significant change in concentration of the drugs occurred during the 24-hour test period.