This experimental study investigated the effectiveness of structured Web-Based Bulletin Board (WBB) discussions in improving the critical thinking (CT) skills of learners involved in veterinary distance learning, as well as their attitudes toward learning via WBBs. The two dependent variables were learners' CT skills and their attitudes toward learning via WBBs. The learners' CT skills were examined in different ways: (a) quantitative method: California Critical Thinking Skills Test (CCTST) to holistically investigate the changes in learners' CT skills, and (b) qualitative method: Interaction Analysis Model to investigate learners' interaction patterns in different phases of the WBB discussions. Detailed information about inter-rater reliability, the training of the coders, and the coding process is provided. The findings indicated that structured WBBs significantly improved learners' CT skills and attitudes toward learning via WBBs.