A frequency-doubled Nd:YAG laser at 532 nm with pulse durations of 2, 5, and 10 ms was used to ablate blood clot phantoms. The clot phantoms were prepared with 3.5% (175 Bloom) gel and Direct Red 81 dye to have an absorption coefficient of 150 cm-1. Ablation thresholds were determined by a fluorescent technique using flash photography to detect the gel surface. The threshold was 15 plus or minus 2 mJ/mm2 and corresponded to calculated temperatures of 80 plus or minus 10 degrees Celsius. Ablation efficiency experiments were conducted at 20 mJ. Ablation efficiencies were approximately 1.7 plus or minus 0.1 (mu) g/mJ for the millisecond pulses and were comparable to previously published efficiencies for ablation of clot with a 1 microsecond pulsed dye laser.