Two references to a record structure conflict if they access the same field and at least one modifies the location. Because structures can be connected by pointers, deciding if two statements conflict requires knowledge of the possible aliases for the locations that they access. This paper describes a dataflow computation that produces a conservative description of the aliases visible at any point in a program. The data structure that records aliases is an alias graph. It also labels instances of structures so that the objects referenced at different points in a program can be compared. This paper shows how alias graphs can be used to detect potential conflicts.