Markets are public spaces in which many kinds of products are sold, as well as places of cultural information exchange. These spaces are distinctive for each given culture or society as they represent small-scale reproductions of that region's cultural and biological diversity. We carried out ethnobotanical studies in an important traditional market in the city of Recife (Pernambuco, northeastern Brazil) in two distinct years, 1995 and 2002. Our objectives were to compare the taxonomic richness of the plants being sold there in these different years, to investigate differences between the species' relative importance, and to present descriptions of their main uses. Considering the lack of ethnobotanical studies in these markets and the great methodological difficulties in gaining access to this type of information, we discuss the limitations of this kind of study and offer suggestions to deal with specific problems. Semi-structured interviews with the plant vendors were carried out in the market, along with other data-collection and analysis techniques common to ethnobotanical studies. A total of 136 species were recorded--an increase of 58 species between the two study periods--with significant differences among the proportions of families, genera, and species (p<0.05). Despite differences in the relative importance of species found in both surveys, there was an underlying trend maintaining the same species of greatest importance. Our data suggest that markets conserve their basic repertoire while at the same time act as open and dynamic systems that is enriched by adding new plants and their respective use-indications.