This dissertation explores the second language acquisition of Mandarin Chinese tones by speakers of non-tonal languages within the framework of Optimality Theory. The effects of three L1s are analyzed: American English, a stress-accent language; Tokyo Japanese, a lexical pitch accent language; and Seoul Korean, a non-stress and non-pitch accent language. The study tests for three possible sources of L2 tonal errors; namely, 1) universal phonological constraints (i.e. the Tonal Markedness Scale (TMS), the Obligatory Contour Principle (OCP), and Tone-Position Constraints (TPC)); 2) the transfer of L1 pitch patterns; and 3) a pedagogical problem of Tone 3. The data shows that these three factors jointly shape the properties of interlanguage grammars. This study finds that the TMS, the OCP, and TPC constrain L2 tone acquisition, but do so to varying degrees. Evidence is found that the TMS applies to both word- and sentence-level L2 productions. Some effects of the OCP are found to interact with the TMS and with L1 transfer effects. For example, patterns regarding tone pairs (more T1-T1 productions than T4-T4, and in turn more than T2-T2) can be attributed to either a case of the "emergence of the unmarked" interacting effects of the TMS and the OCP, or to local conjunction of the TMS. Learners are better at maintaining Rising (T2) at word-initial positions, but Falling (T4) at word-final positions. L2 learners often substitute other tones for target tones and the substitution patterns provide evidence for L1 transfer. For example, English speakers often use high falling tone while Japanese speakers tend to lengthen low tones to express monosyllabic narrow focus in sentences. This study found conflicting error and substitution patterns pertaining to Tone 3, as well as greater accuracy in processing Pre-T3 sandhi than the sandhi occurring elsewhere. This effect is argued to be attributed to the "T3 [214]-First" teaching method. In light of the three factors affecting L2 tone acquisition, this study proposes a constraint re-ranking model to provide a new way of viewing positive and negative transfer. It is demonstrated that some markedness constraints are promoted while some are demoted in the acquisition of tones. [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.]