Recording dynamic information for only a subset of program entities can reduce monitoring overhead and can facilitate efficient monitoring of deployed software. Program entities, such as statements, can be monitored using probes that track the execution of those entities. Monitoring more complicated entities, such as paths or definition-use associations, requires more sophisticated techniques that track not only the execution of the desired entities but also the execution of other entities with which they interact. This paper presents an approach for monitoring subsets of one such program entity---acyclic paths in procedures. Our selective path profiling algorithm computes values for probes that guarantee that the sum of the assigned value along each acyclic path (path sum) in the subset is unique; acyclic paths not in the subset may or may not have unique path sums. The paper also presents the results of studies that compare the number of probes required for subsets of various sizes with the number of probes required for profiling all paths, computed using Ball and Larus' path profiling algorithm. Our results indicate that the algorithm performs well on many procedures by requiring only a small percentage of probes for monitoring the subset.