BACKGROUND: Many instruments are used for laparoscopic dissection, including monopolar electrosurgery scissors (MES), electrothermal bipolar vessel sealers (BVS) and ultrasonically coagulating shears (UCS). These three devices were compared with regard to dissection time, blood loss, safety and costs. METHODS: Sixty-one consecutive patients undergoing laparoscopic left-sided colectomy were randomized to MES, BVS or UCS. The primary endpoint was dissection time. RESULTS: Patient and operation characteristics did not differ between the groups. Median dissection time was significantly shorter with BVS (105 min) and UCS (90 min) than with MES (137 min) (P < 0.001). With BVS and UCS, significantly fewer additional clips were required (MES 9 versus BVS 0 versus UCS 3; P < 0.001) and there was a trend towards lower blood loss (125 versus 50 versus 50 ml respectively; P = 0.223) and a reduced volume of suction fluid (425 versus 80 versus 110 ml; P = 0.058). Overall satisfaction was similar for the three instruments. Dissection with BVS and UCS was significantly cheaper than with MES, assuming a centre volume of 200 cases per year (P = 0.009). CONCLUSION: BVS and UCS shorten dissection time in laparoscopic left-sided colectomy and are cost-effective compared with MES.