Investigations were conducted regarding the acoustical characteristics of existing auditoria built before 1975. Discussions of the historical evolution since Japanese occupation were followed by architectural and acoustical analysis of 21 cases. Although many auditoria built during Japanese occupation were not designed for musical performances, they are more reverberant but smaller than the ones built after World War II. However, 62% of the selected cases were constructed with windows with 4 mm or thinner glazing on sidewalls or around the upper perimeter. Analysis of two auditoria were made regarding the performances of room acoustics, background noise control, and sound system. The room acoustics in both auditoria are suitable for chamber music but are too dry and too loud for orchestra music. Average background noises reach NC40 with AC off and NC50 with AC on. Both sound systems could not give correct directions of sound images, although they provide acceptable output level (96 dB SPL) and speech intangibility (STI 0.57) in the 2000-Hz band. With growing concerns about energy preservation in Taiwan, the current study could provide useful information for renovating or remodeling an existing auditorium. [Work supported by the National Science Foundation of Taiwan.]