Faecal oocyst counts during subclinical intestinal coccidiosis demonstrated clear correlations between the parasite levels in the does and those in their respective litters. In the does, pregnancy did not seem to have an effect on the course of infection, whereas the effect of season was much greater. Intestinal coccidiosis was found in all the young rabbits examined from the start of the third week of life. However, after a phase of great fluctuation in the parasite levels in the faeces, a phase which extended over the initial period of weaning, the infection tended to become stabilized at extremely moderate levels that permitted an optimum state of health and high productivity.