Forty-three samples of piroxicam capsules imported or manufactured by local pharmaceutical factories in Taiwan were randomly collected via local health authorities. These samples were analyzed to evaluate their qualityby virtue of dissolution testing. The analysis included four tests according to the methods of United States Pharmacopoeia XXⅡ The results showed that all samples met requirements for weight variation test. Fourteen percent of the samples failed to pass the dissolution test. Factors which affect the dissolution were analyzed on piroxicam capsules formulated and produced in this laboratory. It was shown thatexcipients have certain degree of effect on the dissolution. The dissolution rate was reduced if the capsule contains more than 5% of magnesium stearate. This may be due to the lamination and subsequent adhesion of piroxicam to the dry agglomerate. The mixing time of magnesium stearate didnot have a significant effect on dissolution. It was also found that 0.75% and 1.56% of sodium lauryl sulfate increased the dissolution rate of piroxicam capsules. Higher concentration of sodium lauryl sulfate(3.12%) decreased the dissolution rate. However, sodium lauryl sulfate is not recommended for oral formulation.