Experimental methods are presented for determining the thermal resistance of vertical-cavity surfaceemitting lasers (VCSELs) and the lateral electrical conductivity of their p-type semiconductor layers. A VCSEL structure was manufactured from III-As compounds on a gallium arsenide substrate. Conductivity was determined using transmission line measurement (TLM). Electrical and thermal parameters were determined for various ambient temperatures. The results could be used for computer analysis of VCSELs. Keywords: TLM, thermal resistance, VCSEL, AlGaAs.