Through an English for Specific Purposes (ESP): Communication in Nursing online course, the present study examines the efficacy of synchronous voice-based and text-based chats as instructional and communicative modes in learning to use open questions for probing in therapeutic dialogues by non-native speaking (NNS) participants, students of a nursing college at a major university in the Philippines. The study draws on a plethora of research findings in online education, ESP online course designs, text-based vs. voice-based synchronous chats and their place in learning online, efficacy and application of text and voice-based communicative practices in online courses designed for NNS students, issues related to medical discourse, humanization, and patient-centeredness of communicative encounters (e.g., between a nurse/provider and a patient/client). The study examines the following questions: (1) which interactional mode--voice or text--provides for better learning of probing questions by NNS medical professionals through noticing of their use in therapeutic dialogues and situations typical for everyday healthcare-related communicative settings in an online course; (2) what evidence is there to suggest that the skill to use open questions for probing in role-plays of therapeutic dialogues by NNS medical professionals developed through text-based practices in an online course might transfer to their speech and vice versa; (3) which interactional mode--voice or text--is perceived by the online-course participants as more effective for learning to use probing questions in therapeutic dialogues and healthcare-related communicative encounters. The results of the analyses supported many of the hypotheses for both research conditions. More specifically, they supported the predicted efficacy of both forms of online instruction and communication--voice-based and text-based--in learning probing techniques by the online course participants; furthermore, a possibility of the two-way language-skill transfer modes--from text-to-speech and from speech-to-text--was suggested in learning second language online through application of synchronous chat sessions. Although more research is necessary in the above-mentioned areas of language learning in the context of online education, the research findings of the present research study are highly suggestive of effective implementation of voice-based and text-based synchronous chats in ESP online course designs for NNS speaking students. [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.]