For the first time, new sets of experimental data are reported on the particle collection efficiencies of modified surface body cyclones namely, spiral guide body, circumferential groove body, and vertical groove body cyclones. Five different cyclones were studied covering a flow rate range of 15 to 80 l/min. Experimental particle collection curves of the conventional cyclone were compared with those predicted using several cyclone efficiency theories. For each flow rate, the Dietz's theory was found to predict the experimental results most accurately. The present study shows that the spiral guide can help enhance collection efficiency at low flow rates. However, at high flow rates, the guide no longer plays an important role in cyclone collection efficiency. It is also shown that groove body cyclones are less efficient than conventional cyclones. As expected, the 50% cut diameter decreases and the decline in pressure is seen to become larger as the flow rate increases for all cyclones tested.