The effects of four directly compressible excipients such as Avicel, Dipac, Ditab and Emdex on the stability of ascorbic acid tablets were evaluated. Ascorbic acid tablets were formulated by the direct compressive method at constant temperature and pressure. In vitro tablet properties such as weight uniformity, hardness, friability, moisture content, disintegration time and dissolution rate were evaluated. The tablets were also subjected to temperature and moisture stresses in order to assess their stability. The results obtained indicated that moisture and temperature affect the stability of ascorbic acid tablets. All the tablet batches exhibited very short shelf lives in the presence of the stress conditions of temperature and moisture. None of the four excipients could be recommended for use in tableting ascorbic acid based on the shelf lives.