We present our investigation of the optical limiting behaviour of different metal and semiconductor nanoparticles in liquid and solid media. Nonlinear transmission measurements were performed by the use of nanosecond laser pulses at 532 nm and 1064 nm. For the various nanoparticles in liquid media large differences in the limiting response were found. Foremost the solid state samples are promising in terms of laser protection devices.© (2009) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.