We examined the relationship between growth phase and the initial field strength required for electropermeabilization of yeast cells in suspension. As the period of time for the culture was increased, the initial field strngth necessary for electropermeabilzation of the cells also increased and the slope of the graph of the number of perforations against field strength became smaller. These findings suggest a correlation between growth phase and membrane stength for electric pulses. In "decelerated growth phase", there may have been a greater overall increase in membrane strength than in the case of "exponential growth phase". In a further, "resealing" experiment, observations lead us to conclude that differences in the growth phase of Saccharomyces cerevisiae tended not to influence the rate of membrane resealing.