Data from a number of sequential alternation experiments for 125 subjects were factor analyzed to determine the number of common factors present. Three measures (mean latency of convulsion, mean number of trials to, six convulsions, mean duration of convulsions) were evaluated by principal components analyses. The presence of two factors was suggested in the latency, criterion, and duration measures (primary site stimulation, secondary site stimulation). The two factors were more clearly defined for the latency data than for the other measures. Further analyses with individual trials (rather than means) for the 125 subjects provided approximately the same results. Factor analyses of data from 35 rats stimulated only on one side showed the presence of one factor in all analyses. These results suggest a two-factor interpretation of kindling events, possibly the two effects of Goddard et al. and McIntyre and Goddard: a long-term neurological circuitry modification for each of the primary and secondary sites and a short-term aftereffect which accounts for the negative-transfer aspects from the primary to the secondary site.