The present study investigated the relationships among measures of second language proficiency (SLP), foreign language aptitude, and two types of intelligence (verbal intelligence and reasoning). The research had two objectives: (a) to examine the factor structure of several different SLP test scores; and (b) to investigate the relationship between a general SLP factor (G‐SLP) and a hypothetical general cognitive factor (G‐COG) that was assumed to influence foreign language aptitude, verbal intelligence, and reasoning. Several competing hypotheses were tested using structural equation modeling. Participants consisted of 160 Japanese college students studying English as a foreign language.The results supported two models of SLP: one in which several specific trait factors were highly correlated with each other, and another in which these specific trait factors were connected to a higher‐order G‐SLP factor. Because there were only three first‐order specific factors, these two models could not be distinguished from each other. Further investi gation suggested that GSLP and GCOG were not identical, but mutually correlated k0.65). This relationship implies that students' SLP and cognitive abilities were influenced by two distinct, but mutually correlated factors. More than half the G‐SLP variance (58%)could not be explained by the G COG factor. Several suggestions for krther studies are presented.