Serologic procedures were performed in parallel using hydrophilized polystyrene cuvettes and conventional glass test tubes. Consistent and comparable results were obtained with both containers. No significant differences in antibody titer, specificity, neutralization, or elution were observed. The effect of a proteolytic enzyme on red blood cell antigen was not altered by the hydrophilized plastic tubes. There was no difference in the stability of immune sera stored in glass or plastic at 4 degrees C and--30 degrees C. However, hemolysis of stored red blood cells was significantly slower in the hydrophilized plastic cuvettes.