We present dc-magnetization acid ac-susceptibility measurements of the organic superconductors κ-(ET) 2 X with X = I 3 , Cu(NCS) 2 , and Cu[N(CN) 2 ]Br. For all investigated materials the lower critical field perpendicular to the highly conducting planes, B c l , tends to zero already 0.5 K below T c . This might be an indication for fluctuation effects of single vortices expected for 2D superconductors. Pinning effects lead to an apparent increase of B c l towards lower temperatures and they play an important role for the temperature and frequency dependence of the irreversibility field B i r r determined by ac-susceptibility.