In this article, we discuss two characteristics of the majority of current behaviour- and molecular-genetic studies of reading ability and disability, specifically, the ascertainment strategies and the populations from which samples are selected. In the context of this discussion, we present data that we collected on a sample of Swahili-speaking siblings from Tanzania. With this sample, we (1) explore the efficiency and practicality of the single proband sibpair design and (2) provide data on the predictability of reading and spelling performance using reading-related componential measures in a novel Swahili-speaking sample. Specifically, we present the selection criteria, discuss the pattern of behavioural and behaviour-genetic results obtained on the sample and compare these results with those available in the literature. We report behavioural and behaviour-genetic correlations in this sample that are comparable with other studied samples in other languages, and discuss the similarities and differences. Thus, we demonstrate the suitability and effectiveness of the single sib ascertainment method for genetic analyses of reading ability and disability in novel samples in previously unstudied languages.