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The effect of trona on the fermentation of roselle calyces was evaluated. The addition of trona to the calyces raised the initial pH from 3.3 to 5.3. The important microorganisms of roselle calyces fermentation were enumerated, isolated and identified. The fungi isolated consist of one yeast identified as Saccharomyces cerevisiae and two moulds, Apergillus niger and Aspergillus flavus. Of the aerobic bacteria, only Escherichia coli, Bacillus subtilis and Klebsiella sp. were isolated. The total titratable acid (TTA) value increased throughout the fermentation (0.027-0.043). The nutritional evaluation showed that there was an increase in the protein (6.56%), lipid (4.25%) and carbohydrate contents (74.33%) of the fermented sample with a higher ash content (4.54%) in the unfermented sample. The mineral contents (PPM); Zn (31.86), Fe (12.35), Mg (132.00), Ca (294.31), Na (214.62) and K (382.13) of the fermented sample were generally low. This study reveals that trona can be used to neutralize the acid in roselle calyx and that fermentation can greatly influence the nutritional composition positively. Keywords: Roselle, calyces, Trona, nutritional evaluation, fermentation J Food Tech in Africa (2002) 7, 75-77