The effect of temperature on growth rate, uptake of 2-deoxyglucose, and uptake and incorporation of L-leucine is described for six Gram-positive, nonsporing bacteria. The organisms, designated as psychrotrophs because of their ability to grow at 10C, are Listeria monocytogenes, Erysipelothrix rhusiopathiae, Microbacterium thermosphactum, Brevibacterium linens, Lactobacillus buchneri, and Streptococcus faecalis. The complexity of the results illustrates the difficulty of choosing simple criteria for comparing temperature responses of bacteria. However, L. monocytogenes, E. rhusiopathiae, and M. thermosphactum can be grouped together on the basis of low temperature coefficients (less than 1.8) between 10 and 20C for 2-deoxyglucose uptake. This supports the conclusion that cold-resistant sugar-transport systems are among the fitness traits that permit bacteria to grow at low temperatures.