Acanthaceae consist of more than 4000 species that occur primarily in the tropics where radiation of taxa has been extensive in both wet and dry habitats. Honduras is the last political unit in the Mesoamerican region for which a recent treatment of Acanthaceae has been prepared. Field and herbarium studies during the past three years reveal 69 native species of Acanthaceae there, five of which are endemic to the country. These include an undescribed species and 11 species previously unreported from Honduras. Within the country, the greatest concentrations of species are found in three central, mountainous departments (Comayagua, Cortés, and Olancho) which are neither the wettest nor the driest portions of Honduras. Considering its relative size, location in the tropics, and topographic complexity, Honduras is surprisingly depauperate in native species of Acanthaceae. It is second only to Nicaragua in paucity of Acanthaceae based on species per unit of area among Central American countries. Potential geologic, climatic, vegetational, and historical factors leading to the poverty of acanthaceous species in the Honduran-Nicaraguan region of Central America are considered.

Key words: Acanthaceae, floristics, Honduras, Mesoamerica, phytogeography