Current surgical treatment of the frontal sinus disease include external approaches to obliterate or ablate the sinus and both external and transnasal methods to restore drainage into the nasal cavity. The original Lothrop procedure resects the medial frontal sinus floor, superior nasal septum, and intersinus septum, creating a large frontonasal communication. However, as described, the external approach used in this procedure often allowed medial collapse of soft tissue and the stenosis of the nasofrontal communication. This report further relates our experience with the modified transnasal endoscopic Lothrop procedure using suction drills for cases in which frontal recess exploration had failed to relieve obstruction of the frontal sinus. We present an update of the University of Virginia experience in performing the modified Lothrop procedure in 20 patients from 10/93 to 4/95. Our findings over the follow-up period (average 12 months) have verified that this procedure is effective, with a 95% patency rate for the surgically enlarged frontal sinus ostium. When compared to osteoplastic flap with fat obliteration, the modified transnasal Lothrop procedure offers the advantages of a less invasive procedure with a shorter and usually no hospitalization, less morbidity, and the increased ability to evaluate post-operatively for recurrent disease. A patient charge analysis was also performed comparing patients undergoing frontal sinus obliteration during the same time period, revealing an additional benefit of decreased patient costs for the modified transnasal Lothrop procedure. None of our patients experienced complications, and all showed significant improvement, if not complete resolution of their symptoms. Although this procedure has produced favorable results, it should be noted that this procedure is technically demanding and will require further long term follow-up to verify its efficacy and proper role in the spectrum of surgical approaches for the treatment of chronic sinusitis.