Laser balloon angioplasty with Nd:YAG energy has been proposed as a method to seal intimal dissection and prevent elastic recoil after balloon angioplasty. To better define the vessel response to laser balloon angioplasty, its effects on luminal diameter, Indium-111 labelled platelet deposition, and histology were studied in 10 atherosclerotic rabbits. Balloon angioplasty was performed in both iliac arteries and was followed by laser balloon angioplasty in only one iliac artery. The nonlased artery served as a control. Single (15-35 W for 20 sec) or repetitive laser pulses (12-25 W for 20 sec x 3) were used. Platelet deposition was quantified 2 hr after the intervention. Lumen diameter (mm) increased following balloon angioplasty from 0.99 +/- 0.47 (mean +/- SD) to 1.92 +/- 0.43 and 0.89 +/- 0.46 to 1.99 +/- 0.57 in the balloon and laser-treated arteries, respectively (P < 0.001 for both groups for comparisons to baseline, P = NS for between groups comparison). Laser balloon angioplasty resulted in a further increase in luminal diameter to 2.42 +/- 0.53 (P < 0.02) when compared to the post balloon angioplasty diameter. Platelet deposition (10(6)/cm vessel) was higher following laser balloon angioplasty (26.9, 10.2-189; median range) than after balloon angioplasty (10.6, 3.4-30), P < 0.001. Histologic evidence of laser "sealing" was present in only one artery. Thus although laser balloon angioplasty results in an improved lumen diameter, it is accompanied by increased platelet deposition. In the atherosclerotic rabbit model, abolition of vascular recoil rather than "sealing" seems to be the most important advantage of laser balloon angioplasty over conventional balloon angioplasty.