While the effects of high-intensity laser energy on tissue were studied early in the development of the laser, the interactions of laser radiation with immersion media have been the subject of more recent investigations. Prompted by reports of severe, morphologically unusual dissections occurring during 308 nm excimer laser angioplasty, several investigators have now demonstrated that both blood (haemoglobin) and angiographic contrast media strongly absorb excimer laser light at 308 nm. Upon absorption, this light energy is converted into rapidly expanding and imploding cavitation bubbles that generate intense pressure pulses. Subsequently, several techniques to remove contrast and dilute blood in the ablation field were evaluated. The application of saline infusion has resulted in improvements in both angiographic and clinical outcomes. The purpose of this paper is to review the development and application of the technique of saline infusion in the clinical practice of excimer laser coronary angioplasty.