A drainable ostomy pouch having sidewalls of flexible sheet material defining a cavity therebetween and a downwardly-extending neck portion terminating in a discharge opening that is closed by folding the neck portion upwardly and opened by unfolding the neck portion downwardly. Each of the sidewalls of the neck portion is provided with a transversely-extending bias member that is formed of stiff but flexible, springlike plastic material. The bias members are normally flat so as to be in straight parallel closed condition but are openable under inwardly-directed finger pressure applied to their opposite ends to cause them to bow outwardly away from each other. The pouch also includes a two-part fastening system for holding the neck portion in upwardly-folded condition, the system including a first fastener part located along the outer surface of one of the sidewalls of the neck portion and a second fastener part located along the outer surface of the other sidewall of the neck portion, the fastener parts having outwardly-projecting interengageable locking elements that are brought into interlocking engagement when the neck portion is fully folded.