Tapai is a well-known indigenous fermented alcoholic beverage among Kadazan-Dusun-Murut (KDM) ethnics during festive occasions and gatherings in East Malaysia. Unfortunately, very little research has been done on this beverage. The objective of this study was to identify functional microfloras involved in the production of tapai. Samples from local producers were obtained for microbiological and proximate analysis. The fermentation process was predominated by yeasts and lactic acid bacteria (LAB) with initial numbers (CFU/g) of 10^5 and 10^6, respectively, which gradually increased during the first 2 weeks fermentation but decreased thereafter. The yeasts were identified as Sacchromyces cerevisiae, Candida krusei, C. pelliculosa, C. guillermondii, C. magnoliae and Rhodotorula glutinis, whereas the LAB were Lactobacillus brevis, L. plantarum, L. collinoides and Pediococcus sp. Moulds and Enterobacteriaceae were only present during the first 2 days of fermentation. Acetic acid bacteria were not detected throughout the entire process. The pH of tapai declined slowly from 6.6 to 3.4 in 14 days, and then showed an increment to 4.0. On the other hand, titratable acidity (as % lactic acid)increased from 0.06 to 0.86 in 10 days, and then decreased to 0.82 at the end of the fermentation process. Alcohol was produced and the content can reach as high as 12.3% after 3 weeks fermentation. Proximate composition analysis showed that the moisture content in the end product was 61.8±6.1% whereas ash, protein, fat and crude fiber (of dried samples) were 0.50±0.1%, 8.7±0.1%, 0.29±0.01% and 0.56±0.03%, respectively.