We evaluated particulate and microbial contamination in a total of 192 samples of in-use admixed and unadmixed parenteral nutrition solutions remaining in infusion bags in 10 hospitals. The mean numbers (range) of drug glass ampoules, plastic ampoules, and vials used in a total of 192 admixed solutions were 3.38 (1-13), 0.79 (0-7), and 1.2 (0-8), respectively. The mean number of particles (range) contained in the 192 samples according to the particle size (diameter) was 960.9 (30-9,539)/ml for particles >or=1.3 microm, 42.8 (0-587)/ml for those >or=5 microm, 6.4 (0-146)/ml for those >or=10 microm, and 0.09 (0-1)/ml for those >or=50 microm. The number of particles >or=1.3 microm in diameter was significantly higher in the 192 samples than in 7 samples (controls) of solutions not mixed with any ampoule or vial (p<0.0001). In addition, the number of particles >or=1.3 microm in diameter was significantly higher in samples of solutions mixed with 4-13 glass ampoules than in those of solutions mixed with 1-3 glass ampoules (p<0.01). On the other hand, none of the 199 samples showed bacteria or fungi/5 ml residual solution. Measures against particulate contamination of admixed parenteral nutrition solutions are necessary.