Drought is one of the most important factors limiting crop production in sub-Saharan Africa. This has detrimental effects to the people living in this region, and whose population is increasing more rapidly than their domestic food production. Noticeably, pressure on agricultural land has continued to intensify. Cassava is one of the staple crops with remarkable tolerance to drought. It is adapted to diverse and poor soil conditions, in addition to its flexibility in planting and harvesting times. Understanding its physiological and molecular basis of drought tolerance may help to target the key traits that limit crop yield under drought conditions. To improve our understanding on drought tolerance mechanisms in cassava, the project 'Identifying the physiological and genetic traits that make cassava one of the most drought-tolerant crops' was initiated in 2005 by the Brazilian Agricultural Research Corporation (Embrapa) in collaboration with the International Center for Tropical Agriculture (CIAT); the International Institute of Tropical Agriculture (IITA); Cornell University and University of Goettingen. The ultimate goal of the project was to identify morphological, physiological and molecular traits related to drought tolerance mechanisms in cassava for further progress, and for their application in cassava and other crop breeding programs. The present study was conducted within the framework of this project with 31 African cassava germplasm accessions from IITA and a mapping population developed at CIAT. The objectives of this study were, 1) To develop a protocol for hardening and rapid micro-propagation of cassava plantlets under local, low-cost conditions; 2) To identify agro-morphological attributes that are related to drought tolerance in cassava; 3) To identify drought-tolerant and drought-susceptible cassava germplasm from a selection of African accessions; 4) To identify secondary traits that could be used for phenotyping breeding materials for drought tolerance; 5) To screen the CIAT mapping population with simple sequence repeats (SSR) and expressed simple sequence repeat (ESSR) markers for linkage analysis. Thirty one putative drought-tolerant and drought-susceptible African cassava germplasm accessions from IITA were micro-propagated using direct and in-direct techniques, at Kenya Agricultural Research Institute (KARI), Nairobi, Kenya. In direct micro-propagation, plantlets were hardened using vermiculite and multiplied through nodal cuttings. In in-direct micro-propagation, plantlets were first multiplied through sub-culturing and later hardened. The direct micro-propagation method had a higher multiplication rate. The number of plantlets obtained in 7 months using the direct method were 1173 as compared to 722 attained using the in-direct micropropagation. Rapid micro-propagation through nodal cuttings was cheaper in terms of consumables and an effective alternative to enhance rates of multiplication, over the in-direct method and the more conventional technique like the use of stem cuttings. Agronomic and morphological evaluation of contrasting African cassava germplasm accessions was carried out in water-stressed and well-watered environments at 5 time points. The trial was conducted at the experimental field of KARI, Kiboko Research Station in Makindu, Eastern Kenya, a site characterized by Acri-orthic Ferralsol soil. Analysis of variance was performed using the agronomic and morphological data, and broad sense heritability was estimated. In general, significant differences were observed among the accessions, suggesting a strong genetic basis for the phenotypic variation observed. Variation was also notable in water-stressed and well-watered environments for a majority of traits evaluated. This was due to the artificial water applied since, during the trial period, there was hardly any rainfall. At harvest, leaf length and width of certain acc