Thermal alterations of tissue as they relate to the initiation of continuous wave (cw) laser ablation were investigated. Porcine aorta samples were thermally altered in 160°C to 200°C glycerine baths and subsequently subjected to argon laser irradiation (488 - 514 nm). Experimental limitations, which resulted in slight compression and dehydration during heating, were accounted for with control samples. During laser irradiation, an infrared camera was used to infer thermal events associated with laser ablation of the heated, control, and untreated samples. Although changes in optical and thermal properties could not be isolated, temperature histories revealed statistically faster heating rates for samples in which more than about 6% water loss occurred during pre-treatment. Further, surface temperature recordings documented the explosive nature of cw laser ablation of soft biological media and demonstrated similar ablation threshold temperature ranges (170°C to 230°C) for most samples. The exceptions, tissue samples treated in a 200°C bath, did not display explosive ablation onset. Results suggest that temperature dependent mechanical properties of the tissue can be significantly degraded during heating and appear to dictate ablation initiation.