This descriptive study analyzed the emergence of the imperfect in the written production of 30 beginning learners of Spanish. The analysis focused on the use of the imperfect and the morphological marking of state verbs. The results follow the patterns predicted by the aspect hypothesis (Andersen and Shirai, 1994), and support some refinements of the proposed stages of spread of the imperfect across aspectual classes. A detailed analysis of the category of state verbs showed that these verbs do not behave as a homogeneous category with regard to past tense marking. The possibility of the application of associative mechanisms of learning (Pinker and Prince 1994) was explored based on the past tense marking of irregular and regular verbs in connection to the stages of acquisition proposed by the aspect hypothesis, but not enough evidence was found to strongly support the application of such learning mechanisms.