A Q-switched frequency-doubled Nd:YAG dye laser, configured to emit light at 577 nm, was used to study the effect of nanosecond pulsed light on vascular tissue. The pulse width of this light is approximately 10 nanoseconds and the pulse repetition rate is, at most, 10 Hz. A rat dorsal skin-flap window-chamber model, a colon (cecum) model, as well as an isolated femoral vessel model were used to study the effects on vascular tissue of irradiation with single laser pulses using fluences ranging from 0.2 J/cm2 to 3 J/cm2. Different reactions such as vasospasm, vessel expansion, and vessel rupture were observed. A correlation between increasing fluence and increased vascular damage was noted. When it occurred, vessel rupture was seen on the superior side (i.e. the irradiated vascular surface) as well as on the inferior side of the blood vessel. The inferior side damage was verified on histological examination. This damage pattern was thought to be most likely caused by shockwaves, and photoacoustic measurements were performed that support this hypothesis.