Time pressure is prevalent in the software industry in which shorter and shorter deadlines and high customer demands lead to increasingly tight deadlines. However, the effects of time pressure have received little attention in software engineering research. We performed a controlled experiment on time pressure with 97 observations from 54 subjects. Using a two-by-two crossover design, our subjects performed requirements review and test case development tasks. We found statistically significant evidence that time pressure increases efficiency in test case development (high effect size Cohen’s d=1.279) and in requirements review (medium effect size Cohen’s d=0.650). However, we found no statistically significant evidence that time pressure would decrease effectiveness or cause adverse effects on motivation, frustration or perceived performance. We also investigated the role of knowledge but found no evidence of the mediating role of knowledge in time pressure as suggested by prior work, possibly due to our subjects. We conclude that applying moderate time pressure for limited periods could be used to increase efficiency in software engineering tasks that are well structured and straight forward.