This dissertation compares the knowledge of Russian Verbal Aspect in two types of learners enrolled in college level Russian courses: foreign language learners of Russian whose native language is English and heritage language speakers of Russian whose dominant language at the time of study is English. Russian Aspect is known to be problematic both for monolingual and bilingual children acquiring Russian and adults acquiring Russian as second/foreign language (Kazanina & Philips 2007, Anstatt 2008, Gupol 2009, Slabakova 2005b, Nossalik 2009). Recent studies have also shown that aspect may not be completely acquired by Russian heritage speakers of low and even near-native proficiency (Polinsky 2008, Laleko 2010). In my study, advanced proficiency English dominant heritage and foreign language speakers of Russian show an asymmetry in their comprehension of lexical and grammatical aspect. I show that the semantics and syntax of aspect are acquired; however aspectual morphology plays both a facilitative and a hindering role in the comprehension of aspectual distinctions. Two experimental tasks manipulated pairs of sentences differing in aspectual interpretation based on presence/absence of a telicizing prefix or presence/absence of an imperfectivizing suffix. Based on the results, I argue the difficulties that advanced proficiency foreign language learners and heritage speakers have with Russian Verbal Aspect are not the result of a diverging grammar (rules of aspect formation) but can be attributed to reduced lexical and morphological knowledge as well as processing limitations. I find that English processing strategies may interfere with the processing of Russian aspect by both potentially incomplete acquirers, but at advanced proficiency level, heritage speakers have advantage over foreign learner learners in interpretation and processing tasks. The findings are consistent with Bottleneck Hypothesis (Slabakova 2008), which assumes functional morphology to be a tight spot in second language acquisition and acquisition of syntax and semantics to be unproblematic. I propose, following Polinsky 2011, that functional morphology can be seen as an acquisitional bottleneck for heritage language speakers as well. In addition, as Montrul 2009, I have found that heritage speakers have advantage over foreign language learners in the acquisition of grammatical aspect, but not necessarily of lexical aspect. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]