GaN nanowires as a group III-nitride semiconductor offer an interesting potential for optoelectronics and nano-electronics devices running at ambient temperatures. We report on recent investigations on the realization of electric contacts on p-doped GaN nanowires. After growth of the NW by molecular beam epitaxy with in situ Magnesium doping we define individual metal source-drain electrodes by electron-beam lithography. We study the characteristics of different metal contact material combinations. The fabricated contacts and the influence of rapid thermal annealing steps are characterized by IV-measurements at room temperature. We find that Ti/Au contacts commonly used for n-type GaN exhibit poor contact properties in contrast to combinations using Ag or Pd to contact the wire.