There was a 1000-fold difference between the highest and the lowest mean rate of dispersal of bacteria-carrying particles during exercise among a group of three male and three female subjects. Differences in the numbers of skin fragments dispersed and in the proportion of these carrying bacteria were almost equally responsible for this. Since there is little difference between individuals in the rate of skin replacement the differences in the rates of dispersal of skin fragments during exercise must reflect large variations in the amount of skin surface removed in other ways. The skin fragments dispersed had a wide size range extending below 5 micrometer for the minimum projected diameter (MPD). The median MPD was about 20 micrometer with 7-10% less than 10 micrometer. Many of the particles could therefore pass freely through tightly woven fabrics with pores up to 10-15 micrometer which might seem to be impenetrable to whole corneocytes, typically larger than 30 X 40 micrometer in the hydrated state.