My thesis investigates the bilingual lexicon and lexical access in single word production. Successive Swedish/Spanish speaking adults with different proficiency levels are tested on two picture-word interference tasks. In short, the results contributes to the understanding that many factors contribute to the way a second language is processed. Length of immersion, typological distance between first and second language as well as how many languages a person knows besides the two languages tested. All these factors must be given careful consideration in any psycholinguistic study of the bilingual lexicon.