Bostryx is largely distributed in Andean Valleys and Lomas formations along the coast of Peru and Chile. One species, Bostryx aguilari, is restricted to Lomas formations located in the Department of Lima (Peru). The use of genetic information has become essential in phylogenetic and population studies with conservation purposes. Considering the rapid degradation of desert ecosystems, which threatens the survival of vulnerable species, the aim of this study was, first, to resolve evolutionary relationships within Bostryx and to determine the position of Bostryx within the Bulimulidae, and second, to survey the genetic diversity of Bostryx aguilari, a species considered rare. Sequences of the mitochondrial 16S rRNA and nuclear rRNA regions were obtained for 12 and 11 species of Bulimulidae, respectively, including seven species of Bostryx. Sequences of the 16S rRNA gene were obtained for 14 individuals (from four different populations) of Bostryx aguilari. Phylogenetic reconstructions were carried out using Neighbor-Joining, Maximum Parsimony, Maximum Likelihood and Bayesian Inference methods. The monophyly of Bostryx was not supported. In our results, B. solutus (type species of Bostryx) grouped only with B. aguilari, B. conspersus, B. modestus, B. scalariformis and B. sordidus, forming a monophyletic group that is strongly supported in all analyses. In case the taxonomy of Bostryx is reviewed in the future, this group should keep the generic name. Bostryx aguilari was found to have both low genetic diversity and small population size. We recommend that conservation efforts should be increased in Lomas ecosystems to ensure the survival of B. aguilari, and a large number of other rare species restricted to Lomas. © 2013 Sociedade Brasileira de Zoologia.