Although polyaniline (PAni) has been proposed for use as a hole injection layer (HIL) in organic light emitting diodes (OLEDs) and polymeric light emitting diodes (PLEDs) from very early on, the material does not seem to have found widespread use on a (pre)commercial scale. Recent results will be presented showing that PAni can be efficiently used as HIL, and that it even has some advantages over the often preferred poly [ethylenedioxy-thiophene] (PEDT). Intensive investigations on the influence of conductivity, morphology and especially the work function onto device performance have led to a commercially available water-borne PAni dispersion. The stable, nanoscaled system for HILs has a particle size of about 35 nm and a lateral conductivity (when deposited and dried) of around 10^-6 S/cm. Using PAni dispersions for the generation of HILs the final device performance in OLEDs and PLEDs could be significantly improved. Depending on the used light emitting polymer (LEP). luminescence data were up to 30% more efficient compared to devices made with the widespread used PEDT.