Two-hybrid systems are powerful tools to find new partners for a protein of interest. However, exchange of material between two-hybrid users has been handicapped by the various versions of two-hybrid systems available and by the widely accepted idea that they are not compatible. In the present paper we show that, contrary to the dogma, the most often used two-hybrid systems may be combined by either transformation or mating assays. The protocol to be followed in each case is provided. This will greatly increase the prospects of the growing network of interacting proteins, by reconciling the "two-hybrid systems" and the "interaction trap".