Abstract: This invention relates to improvements in pressure core barrels of the type described in U.S. Pat. No. 3,548,958 wherein a controlled pressure is maintained on a core sample during surfacing. Among the improvements provided by the present invention are an improved arrangement of the pressure control valve, a device for positively latching the assembly (both in the open and closed positions) and the provision of a hydraulic assist for moving the outer barrel to the sealing position. Another particular feature provides an improved device for flushing drilling mud from the core barrel mechanism with sealing valve open and while the core sample is maintained substantially at a pressure at which it was sealed in the bore hole and to facilitate subsequent freezing and removal of the core sample therefrom for analysis.