The narrow band chaotic output of the self-amplified spontaneous-emission free-electron laser (SASE FEL) exhibits intensity spikes. In the linear regime before saturation, we use an approach developed by Rice to determine probability distributions for the peak values of intensity in both the time and frequency domains. We also find the average number of spikes per unit time or frequency. In addition, we derive joint probabilities for the intensity in the output pulse to have values 1 I and 2 I at times 1 t and 2 t , and for the spectral intensity to have values 1 I and 2 I at frequencies omega(sub 1) and omega (sub 2) .