The study investigates the second language (L2) acquisition of the adjective marker -de(ADJ) in Chinese. It explores the interaction between processing constraints as represented in processability theory (Pienemann, 1998) and the learner's categorial analysis of Chinese adjectives and stative verbs (which cross-categorize) in the acquisition process. An examination of 3 longitudinal L2 data sets revealed more stative verbs (Vstatives) than adjectives in the learners' L2 Chinese. Furthermore, there appeared to be a correlation between the number of adjectives in the L2 samples and the developmental schedule of -de(ADJ). The reasons for the findings were explored through the processing procedures required for the structures in which the adjective and the Vstative occur and the impact they had on learners' categorial analysis of adjectives and Vstatives in L2 Chinese.