Various technologies and techniques are described for providing a transaction grouping feature for use in programs operating under a transactional memory system. The transaction grouping feature is operable to allow transaction groups to be created that contain related transactions. The transaction groups are used to enhance performance and/or operation of the programs. Different locking and versioning mechanisms can be used with different transaction groups. When running transactions, a hardware transactional memory execution mechanism can be used for one transaction group while a software transactional memory execution mechanism used for another transaction group.