The visual compatibility of 30 drug additives with total parenteral nutrient (TPN) solutions (4.25% amino acids, 25% dextrose injection) was studied. For each drug additive, three TPN solutions were mixed; two were stored for 22 hours at 4 C then allowed to equilibrate to room temperature for two hours. Two 25-ml samples from each TPN solution were examined immediately or after 25 hours for visual appearance, particulate matter levels and pH. A microscope was used to count and measure particles filtered from samples on a 0.8-micrometer filter. Only the TPN solutions containing amphotericin B showed any visual discoloration or precipitation. All amphotericin B samples and the 25-hour ampicillin sodium samples exceeded USP particulate matter specifications. Individual particulate matter levels of the other TPN solutions varied but met USP specifications. With the exception of tetracycline hydrochloride, which dropped the TPN solution's pH 0.9 units, the additives had little effect on pH of the TPN solutions (pH 6.45). Amphotericin B and ampicillin sodium were considered visually incompatible with TPN solutions. All other drug additives tested were visually compatible with TPN solutions.