Aloes are used in traditional medicine for arthritis and to treat skin irritations. These indications could point to the plants having anti-inflammatory activity. Methanolic extracts of dried leaves of 53 Aloe species were tested in the cyclooxygenase-1 assay. Cyclooxygenase is one of the key enzymes in the biosynthesis of prostaglandins that are implicated in inflammatory processes. The selected species are representative of all chemotypes identified for the genus. The grass-like and scandent aloes accumulate flavonoids in co-occurrence with the anthrone isomers aloin A and B (A. boylei). This group is considered to be basal in Aloe and with the exception of A. ciliaris, members of this chemotype showed high values of inhibition. The flavanone producing species (A. pratensis, A. humilis and A. pretoriensis) also exhibited high values. These high values are similar to those recorded for aloes which accumulate anthrones and chromones (A. wickensii). The two main anthrone chemotypes in Aloe are represented by homonataloin- and aloin accumulating species. No significant differences could be observed between species accumulating aloin (A. ferox) when compared to the homonataloin-producing species (A. mitriformis). It is interesting to note that species with similar exudate profiles (A. mitriformis and A. comptonii) showed similar values of inhibition.