This article reports on the initial results of the Spanish data from the ICLE Error Tagging Project (Louvain). The corpus consists of 50,000 words of texts (argumentative essays and literature examinations) written by English Philology students at two Madrid universities. The tag categories were: Form (F), Grammar (G), Lexico-grammatical aspects (X), Lexis (L), Word (W), Punctuation (Q), Register (R) and Style (S). All tags were triple checked by various native-speaker raters. The results show that grammar (35%) and lexis (28%) account for two-thirds of the errors, while punctuation accounts for 11%, form 9%, word 7%, lexico-grammatical factors 6% and register and style for 2% and 1%, respectively. The study proposes various areas of investigation which may be useful to others who are working with English-Spanish contrastive data: discourse/pragmatics; semantics; (lexis)/lexico-grammar; syntax; phonetics/writing systems; and non-structural factors (writing conventions).