An IEEE Task Force on Lightning Parameters has completed a comprehensive review of measurements from instrumented towers, supplemented with a survey of indirect results obtained from lightning location systems (LLS). Our goals in writing this paper are to link the Task Force recommendations into IEEE standards related to lightning protection, as well as to point out areas of scientific disagreement and statistical or experimental weakness that can be resolved through additional work. The rationale for simple empirical fits to observations is demonstrated through the use of recommended parameter distributions in engineering case studies to support the development or improvement of lightning protection standards. In contrast to the slow rate of accumulation of data to instrumented towers, there are opportunities for making more effective use of existing and new data from remote measurements using LLS. Analysis in this paper suggests that some objections to LLS-inferred peak current distributions discussed in the Task Force paper may be overstated, and suggests practical studies involving natural first strokes to resolve other questions.