The microbial contamination rate was compared for parenteral nutrition solutions prepared by patients for home use and by pharmacy personnel for inpatient use. Phase I validated the Ivex 0.22‐μm inline filter as a tool for microbiological testing by inoculating small numbers of organisms in 5% dextrose injection and testing for recovery. Phase II validated the same method for determining microbial contamination of total parenteral nutrition (TPN) solutions. Phase III compared inpatient and home TPN microbial contamination rates using the methodology validated in phase II.Test organism inocula used in phase I and II wereCandida albicans, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis,andStreptococcus pyogenes.All contaminated solutions in phase I showed visual turbidity within 48 hr, and all test organisms were recovered and identified.All phase II‐contaminated TPN solutions showed visual turbidity after 96 hr, and all test organisms were recovered and identified.One hundred postinfusion TPN samples were collected randomly during phase III from inpatient parenteral nutrition patients. Six patients and two hospitals participated in the study. None of the 44 home parenteral nutrition samples and none of the 56 inpatient TPN samples developed visible turbidity. Subcultures of each sample on blood agar were negative for microbial growth.This described methodology offers an effective means to establish contamination rates of parenteral nutrition solutions after administration.(Journal of Parenteral and Enteral Nutrition12:25–28, 1988)