A rather simple and general analysis allows calculation of the transient response of many different radiators of practical interest directly in the time domain without the knowledge of the corresponding time harmonic field. Here, we present exact expressions for the transient near-and far-fields around thin circular current loops of arbitrary dimensions involving arbitrarily time-varying excitation. The resulting convolution integrals have been numerically evaluated for “step”-function currents with finite rise time, thus allowing interpretation of the different influence of small and large loops on the transient radiation field. The physical background of the time history of the ideal step-function response is discussed in detail.