A tissue retrieval device includes a tubular member, one or more frame members, and a tissue retrieval bag. The tubular member is insertable into a patient through a trocar to open the bag within the patient to receive a tissue specimen. The internal capacity provided by the bag may vary based on the longitudinal position of the frame members. The bag may be stretchable to increase its internal capacity. At least one sidewall of the bag may include one or more reinforcement members, which may influence the way in which the bag stretches by restricting stretching of the bag in one or more directions while freely permitting stretching of the bag in one or more other directions. Part of the undeployed bag may be contained in a recess formed in the side of the tubular member, with a removable cap being positionable over the undeployed bag and recess.