ABSTRACT: The collection of production performance data in small ruminants pastoralists flocks is essential to evaluate their efficiency and assess how different challenges, such as diseases, droughts or changes in land use, affect their sustainability. Although different methodologies exist, capturing these data is difficult, particularly in nomadic pastoral flocks. In this study, a method for rapid assessment of flock production performance based on farmer recall was designed, implemented and tested. Through literature review and consultation with pastoralists and key informants, a questionnaire was developed to capture small ruminant flock data disaggregated by age (≤2 years old and >2 years old), species and sex. Data on flock dynamics and on reproduction parameters were collected for a period of 12 months. A survey of 130 pastoralists with medium to large flocks was then conducted in Kajiado County (Kenya). Values were calculated for 12 reproduction performance indicators and 7 additional production performance indicators. In addition, a flock efficiency indicator (FEI) is proposed that classifies mixed flocks (i.e., with sheep and goats) into low, medium or high efficiency. Results showed that in flocks with low efficiency, the median value for net fecundity rate was 0.43 lambs/ewe (range 0.08-1.00) and 0.41 kids/doe (range 0.07-0.73), and the median production rate was 6% (range [-47%] to 20%) for sheep and 11% (range [-38%] to 0.21%) for goats. In flocks with high efficiency the median net fecundity rate was 0.77 lambs/ewe (range 0.48-2.73) and 0.88 kids/doe (range 0.49-1.80), and the median production rate was 25% (range 11-47) for sheep and 28% (range 15-46) for goats. Sixty-two (47.7%) of the pastoralists surveyed reported usually buying animals into their flocks, and, consequently were considered as 'pastoralists and traders'. Their flocks had significantly lower FEI scores (median = 7.5, interquartile range [IQR] 6-9), compared with "pastoralists only" flocks (median = 8, IQR 6-10, Kruskal-Wallis rank sum test, p-value <0.001). Since this method is based on pastoralist recall, values obtained should be considered as approximations. Nonetheless, the proposed assessment tool can be used by individuals with low resources or recording capacity, and in large scale programmes to monitor pastoralist flock dynamics, set-up benchmarking programmes, estimate the impact of diseases and shocks, identify those flocks which are most vulnerable to these shocks and evaluate the effectiveness of policies and interventions on herd performance.