A total of 143 sets (281000 hooks) were observed on board two Spanish surface longliners targeting swordfish (Xiphias gladius) during fishing operations in the South East Pacific. Each vessel used a surface longline type (monofilament or multifilament style), including several hook and bait types, previously designed to provide an identical configuration in both vessels. Standardized catch rates were obtained by the Generalized Linear Model using a Deltalognormal approach and observations were restricted to those areas and time periods where the fishing operations of the two gear types overlapped. ‘Gear’ and ‘area’ were the most important factors able to explain both the proportion of positive sets and the catch rates of most of the species captured. Given the special characteristics of this experiment, equivalences between the efficiency of the two longline styles are provided for each of the species under consideration. The monofilament longline showed an efficiency per hook of 1.7, 1.9, 1.3 and 2.0 greater than the multifilament longline for swordfish, blue shark, shortfin mako and billfish, respectively, when their standardized catch rates were considered.