What is the difference between ‘I have done a lot of work this morning’ and ‘I did a lot of work this morning?’ Are sentences such as ‘I have seen him yesterday’ and ‘Who has invented the telephone?’ grammatically correct in present-day English? These are a few examples of the challenges that learners and teachers of English as a second language face when acquiring and teaching tense in English in instructional settings (e.g., grammar classes). The concept of practice as a necessary component for learning a language is a given for many learners and teachers. However, it has received relatively little attention from a theory-based perspective. In the past, much of the instructional practice related to tense in English consisted of mainly output-focused drills, which required learners to produce grammatically correct forms. Although this approach has found its way into contemporary language teaching and has proven useful in its own ways, it has focused almost exclusively on output practice to the exclusion of other forms of practice. Contemporary materials designed for explicit instruction on tense in English have seen changes such as the addition of input-based practice, which requires learners to interact with input without producing any forms. This dissertation addresses the concept of practice by investigating the effects of input practice and output practice on the acquisition of tense by intermediate Dutch-speaking learners of English. It does so by comparing an input processing hypothesis with skill acquisition theory in three computer-controlled learning experiments, involving 216 learners of English.