This experimental study investigates the second language acquisition of the four Mandarin aspect markers -le, -guo, -zhe, and zai- by native Swedish university students enrolled in Chinese language courses in Sweden. The main points of inquiry are acquisition order, the Aspect Hypothesis, the Distributional Bias Hypothesis, and the Prototype Model. The study contains a cross-sectional study and a longitudinal study. Both written and spoken data are collected. The tasks in the cross-sectional study include film-retelling, picture-retelling, grammaticality judgment, fill-in-the-blank questions and comprehension. The longitudinal study includes written data produced by seven students in their tri-monthly journal. The study shows that perfective markers are produced before imperfective markers. The results of the experiments are consistent with the Aspect Hypothesis. The Distributional Bias Hypothesis can account for most of the Aspect Hypothesis but there are exceptions that indicate that other factors could also influence the acquisition process, such as L1 transfer. The Prototype Model cannot be conclusively proven. Apart from contributing to second-language acquisition theo-ries on cross-linguistic tense-aspect morphology, this study can provide empirical evidence with significant pedagogical implications for the second-language learning classroom.