Bacterial and fungal growth in 10% soybean oil emulsion (Intralipid) and 5% fibrin hydrolysate in 5% dextrose was studied at 4, 25 and 37 degrees C. Staphylococcus aureus, Streptococcus pyogenes, Str. fecalis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Candida albicans were grown in broth at 37 degrees C, diluted in saline and inoculated into each of the two preparations as well as a mixture of the two. Growth was measured at 24, 48 and 72 hours. In 10% soybean emulsion, all bacteria except S. pyogenes multiplied, but in fibrin hydrolysate-dextrose solution the only organism of those studied to grow was S. aureus. In the hydrolysate-dextrose-lipid mixture, all organisms multiplied except S. pyogenes and P. aeruginosa. C. albicans grew in all solutions tested. While at 4 degrees C, organisms did not multiply. The fibrin hydrolysate-dextrose solutions given by infusion into a central vein for hyperalimentation have been shown to support predominantly fungal growth, and contamination of the solution and ultimately of the indwelling catheter is a constant hazard. Because both bacteria and C. albicans grew equally well in 10% soybean oil emulsion, its use as a caloric source when infused into a central vein may increase the occurrence of sepsis. When this emulsion is used to provide essential fatty acids or calories, it should be given via a peripheral vein, so that a central catheter will not be contaminated.