This species is characterized by its medium-sized leaves that are tough-textured and rugulose, its ligulate stipules with numerous glands in the upper part, its pedunculate cymose inflorescences with numerous flowers that are sessile in small heads or glomerules, its somewhat small flowers, and its ellipsoid orange-red fruits with smooth pyrenes. Zappi (2003: 580-, fig. 11A-K) presented a description and illustration. She recognized two subspecies, with the typical one widely distributed in dry savanna and cerrado vegetation and the second one with larger leaves, much larger fruits, and a habitat in very wet forest along the Amazon river in eastern Peru. The status of this second subspecies probably deserves re-evaluation now that more material is available. The poorly known species Rudgea krukovii has been synonymized with Rudgea viburnoides by Taylor (1993, Peru Catalogue) and Zappi (2003), but the type locality of this species is in a poorly known area of the southwestern Amazon basin, where several other Rubiaceae are endemic (e.g., Coussarea krukovii Standl.), and these Rudgea plants may deserve re-evaluation as a distinct species.

Plants from the western Amazon basin with robust petiolate leaves, dense hispidulous to hirtellous pubescence, well developed interpetiolar stipules that are laciniate and glandular, short cymose inflorescences with the somewhat small flowers sessile in several glomerules, and markedly large orange fruits have been classified as Rudgea viburnoides subps. megalocarpa. These plants are better documented now, and differ markedly from the typical plants of Rudgea viburnoides in their very large fruits and their habit in very wet forest along the main Amazon drainage. These plants may deserve reconsideration as to their possible status as a separate species. Some plants from the Sierra de la Macarena have been included in herbarium identifications in Rudgea viburnoides subps. megalocarpa, and mature flowers and fruits of these have not been seen but they are vegetatively more similar to Rudgea lanceifolia and are here included in that species. Rudgea viburnoides subsp. megalocarpa is generally similar to Rudgea grandifructa of Pacific coastal Colombia.