Honey of the stingless bee Tetragonisca angustula Illiger, called "angelita" in Colombia, is known to be a valuable folk medicine against different ailments. Scientific data on this honey are rare in the literature. Due to the very low amount of honey produced by a colony and the presumed reputation of healing power, the honey price is high. The antimicrobial activity of angelita honey obtained from Colombia was investigated by means of flow calorimetry and Petridish bioassay on six bacterial and three fungal species. The results were compared with that of Apis mellifera honey from Berlin. The test on the fungal species was done only with the Petridish method. Fungi were not sensitive to the treatments with honey. The bacteria reacted differently with the response not related to their Gram reaction. Honey treated with catalase lost its antimicrobial activity, indicating hydrogen peroxide's remarkable role. Honey concentrations below a critical value resulted in a dense microbial growth around the inhibition zone. Treatments with 20, 10, and 5% dilutions of angelita honey caused inhibition of bacterial growth in the calorimetric experiments. The percentage drop of the power-time (p-t) curve after honey application was dependent on the bacterial species and the concentration of honey used, the higher the concentration the larger the drop. The less sensitivity or even insensitivity of fungi and the promotion of growth by weak honey concentrations should be born in mind while using this honey as an apitherapeutic agent. (C) 2003 Elsevier B.V. All rights reserved.