This book presented an original PhD research submitted to the Faculty of Agronomic Sciences, University of Abomey-Calavi, Republic of Benin in 2006. Indeed, ecosystem and species conservation in the tropics are nowadays the main challenge of forestry research because of habitat destruction and fragmentation. Iroko (Milicia excelsa welw. C.C. Berg), a commercially important timber tree species formerly known by local people in Benin, was subjected to intensive human pressure because of the highly attractive technological properties of its wood and its multipurpose uses. After reviewing the socio-economic importance and ethnobotanical uses of the species in Benin, I assessed structural characterization, morphological and genetic variation in its remnant populations. Therefore, I developed eleven microsatellite primer pairs for the species in order to accurately estimate its genetic diversity and population structure for improved conservation planning. Scientific data collected in this study indicated that M. excelsa populations underwent an effect of isolation by distance and I made some practical suggestions in order to improve in situ conservation of the species.