The XVIIIth General Assembly of URSI was held in Lima, Peru, 8–19 August 1975. Four symposia were held in conjunction with the Assembly: (a) radio waves and ionosphere, (b) nonstationary signal analysis, (c) telecommunications noise and interference environment, and (d) the teaching of electromagnetics and telecommunications science. The organization of these symposia contributed a great deal to the success of the Assembly. The chairmen of the US Commissions were asked to submit brief reports on the scientific highlights in the sessions of interest to their commissions, or to designate others to do so on their behalf. This document is a compilation of those responses, made up of summaries provided by George Birnbaum, Commission I; Alfred H. LaGrone, Commission II; J. M. Kelso, Commission III; D. L. Carpenter, R. W. Fredricks, and C. Russell, Commission IV; Alan Barrett, Commission V; A. A. Ksienski, Commission VI; R. J. Collins, Commission VII; and George Hagn, Commission VIII.