A new horizontal well testing technique, the multipoint interference (MPI) technique, is developed in a single horizontal well. This method is more sensitive than conventional buildup or drawdown tests to reservoir heterogeneities along the horizontal segment of the well. In MPI tests, the fluid is produced at a section or perforations at one end of the horizontal portion of the well and the pressure is recorded at one or more observation points (gauges) at the other end. Solutions of the pressure-transient behavior for spherical fluid flow near a linear discontinuity in a vertically confined formation are developed by using unconventional image theory. The pressure derivative was found to provide distinguishing features for analyzing pressure behavior of MPI tests in a heterogeneous reservoir. The straight-line plot of p vs. 1 root t provides a simple method for analyzing MPI tests. Type curves based on the model developed in this study can be used to determine reservoir properties, such as permeability and porosity, and to detect and locate the reservoir boundaries. The practical utility of MPI tests is demonstrated by several theoretical examples. The solutions developed in this study provide new insight into the pressure behavior of various flow regimes observable in MPI tests. The resulting equations are relatively simple and easy to apply.