Progress in particle correlation studies at NA49

Hambury-Brown and Twiss (HBT) or intensity interferometry is now an important tool in studying the systems formed in Relativistic Heavy Ion collisions. The advances in theoretical understanding of the properties of the correlation function as well as the overwhelming statistical accuracy that large acceptance detectors are now able to provide, give a precise characterization of the source created. The limitations now. instead of being statistical, are in the understanding how the various corrections, and selection criteria affect the results. Some current experimental considerations are detailed. (author)