With the resurgence of thoracoscopy, there is renewed interest in less invasive methods of pleurodesis. We wished to compare in an animal model a variety of methods suggested in reports. The purpose of the study was to rank the effectiveness of each procedure against the standard mechanical pleurodesis. Twenty-five mongrel dogs (weight, 25 to 35 kg) underwent bilateral thoracotomy. Each animal was randomly assigned to receive two of the following methods of pleurodesis: tetracycline, talc, mechanical abrasion, neodymium: yttrium-aluminum garnet (Nd:YAG) laser (Hereus Inc, E. Rutherford, NJ) photocoagulation, and argon beam coagulator (ABC) (Beacon Lab, Bloomfield, CO) electrocoagulation of the parietal pleura. At evaluation at 30 +/- 2 days, the efficacy of pleurodesis was graded on a scale of 0 to 4, with 0 representing a complete absence of pleural symphysis and 4 the adhesion of more than one lobe to both the chest wall and mediastinum. Mean grade and standard deviation of each method were: talc, 3.0 +/- 0.67; mechanical, 3.0 +/- 0.82; tetracycline, 2.3 +/- 1.4; ABC, 1.5 +/- 0.97; and Nd:YAG laser, 0.7 +/- 0.95. Both the talc and mechanical methods were superior to either the Nd:YAG laser or the ABC (p < 0.01). In this study, neither the Nd:YAG laser nor the ABC proved efficacious in producing pleurodesis. Talc poudrage is the only method of pleural symphysis comparable with mechanical abrasion.