The spotted ratfish, Hydrolagus colliei, is a functional intermediate between sharks with gill slits and teleosts with a bony operculum. The ratfish possesses a single gill chamber on either side of its head, bounded by a fleshy opercular flap with a single opening for each chamber located on the underside of the head. Previous studies have reported extremely low ventilation amplitudes consisting of 13-16Pa from the gill chambers of the ratfish. This investigation seeks to further characterize the ventilatory characteristics and patterns from the gill chambers of the ratfish. In addition, this study also seeks to determine if a positive relationship between body size and ventilation amplitude exists. Ventilation pressures were measured from the right gill chamber using implanted pressure transducers. Behavioral observations and amplitude patterns were combined to categorize the pressures into three distinct categories: active, quiet and recovery. Amplitudes recorded in this study were larger than those previously reported with sampled amplitudes averaging around 43Pa and ranging from 21Pa – 78Pa. Due to the close evolutionary relationship between Holocephalans and Elasmobranchs, ventilation amplitudes were predicted to increase with size as seen in a close elasmobranch relative Squalus acanthias. However, smaller ratfish produced amplitudes larger than those produced by larger ratfish which was the opposite of what was observed in Squalus acanthias. Ventilation amplitudes obtained in this study exemplify that the spotted ratfish is capable of generating both low pressures and relatively high pressures in their gill chambers.