The principle that the objects accompanying a burial are in most cases things which were in use at the same time was first stated by J. J. A. Worsaae in 1843. This principle rests on several assumptions, among them that it was customary to place objects beside the dead only at the time of burial, and that the objects so placed were ones owned or used by the occupant or his friends at the time of his death. There is at least one area, the Andean sierra, where we have historical evidence for the renewal of offerings in tombs, and in some cases renewal may have continued periodically for as much as 200 years. In the light of this example it is clearly necessary to determine the burial customs prevailing in the area and period concerned before using grave associations as evidence for contemporaneity. There is also a number of special circumstances which may produce exceptions to the conditions assumed in Worsaae's Law, and to cover the possibility of such exceptions the archaeologist must work with a sufficient number of grave lots so that he can establish rules of consistent association and identify exceptions to them. Worsaae's Law may be extended to state that the objects accompanying a burial were in most cases not only used at the same time but made within a few years of one another. Heirlooms and antiques, the kinds of objects which would not conform to this statement, can be expected to be rare enough so that they would be recognized as exceptions to the prevailing pattern of associations. The evidence of contemporaneity which grave associations provide can be used in two ways. If no stylistic sequence has yet been established for an area, grave associations can serve to check hypothetical sequences suggested on the basis of external evidence. Grave associations provide no evidence of sequence as such, but they do provide a means of testing the validity of the stylistic units or phases which any sequence implies. If a stylistic sequence is already established, the evidence of grave lots can be used to extend it to kinds of materials not included in the original sequence. Fuller utilization of burial associations for both purposes could lead to the solution of many problems in archaeological dating.