The data used in this contribution are taken from the Catalogue (Brako and Zarucchi 1993); by implication, new species and new records for the flora of Peru during the last 10 years are not included in our numbers. Despite these and other limitations described below, we believe that the data are sufficient for the kind of analysis presented in this paper. Data from the Catalogue of the Vascular Plants of Ecuador (Jørgensen and Leo ́n-Ya ́nez 1999) provide a useful perspective on the most species-rich families and the completeness of the data in the Peru Catalogue. Although smaller than Peru, Ecuador is comparable to Peru in the variety of its habitats, which range from semi-deserts, rainforest, and montane forest to pa ́ramo, and it is reasonable to expect that the floras of the two countries are similar. In Table 1 we list the 10 families in Peru with the largest numbers of species in descending order, their species numbers, and the corresponding species numbers from the Catalogue of Ecuador. A quick glance shows that essentially the same 10 families occupy the top 10 positions in both countries, with some changes in the rankings. The two largest families are the same in both countries.