Polyacrylamide gel electrophoresis was used to study homogenate supernatants from the bloodsucking ticks (Argasidae and Ixodidae) belonging to 8 different genera and species. Differences were found in the electrophoretic mobility of protein fractions in adult ticks of these two different families and between several genera of Ixodes ticks (such as Haemaphysalis, Hyalomma, Dermacentor, Rhipicephalus and Ixodes). Argasidae ticks were found to have generic and even species-specific differences at the nymphal stage of development. A. lahorensis nymph-3 contained 5 protein fractions; O. papillipes had 2 fractions, and O. moubata had 3 fractions. Electrophoretic protein separation showed the equal number of protein fractions within one genus of ticks. At the larval stage, the tick homogenates were always found to have one protein fraction. The hemolymph of O. papillipes and O. moubata ticks displayed differences between the imago and nymph-3. A new biochemical marker was proposed to establish a species affinity.