The growth of individual, north Kenyan, pastoralist families' herds of smallstock, given to them in restocking schemes, is followed over several years. Very poor families given similar herds at the start of the project showed great variation in herd sizes by the end of the period analysed. There were highly significant between-year differences in mean herd growth, which appeared to be ultimately caused by climatic variation. But there were no significant between-family effects. That is to say, families that did worse than average in one year were no more likely to do worse than average in another year than was any other family.

The extent to which families depended on income from sources other than their herd is clearly shown to decrease as herd size increases, but families with well over 100 goats were still dependent on some additional source of income for at least 50% of the time.

It is concluded that although families are, in general, managing their herds to the best of their ability, unpredictable livestock mortality is inevitable and will lead to wide variation in household success. The factors causing this variation are largely unavoidable in the environment in which these pastoralists live. Its existence should therefore be accepted and taken into account in the planning and assessment of restocking schemes, and in any other interventions concerning pastoralists' herds.