The dose mean value of specific energy of a single event distribution is related to the variance of a multiple event distribution in a simple way. It is thus possible to determine the dose mean value from measurements in high dose rates through observations of the variations in the ionization current from, for instance, a ionization chamber, if other parameters contribute negligibly to the total variance. With this method it has earlier been possible to obtain results down to about 10 nm ..., which is one order of magnitude smaller than the sizes obtainable with the traditional technique. This advantage together with the suggestion that the dose mean value could be an important parameter in radiobiology make further studies of the applicationns of the technique motivated.