The purpose of this investigation was to determine the diagnostic value (validity) of technetium-99m-pyridoxylideneglutamate cholescintigraphy (99mTc-PGC) in patients with and without cholecystitis and to compare its validity to those of oral cholecystography (OC) and ultrasonography (US). 99mTc-PGC was applied to 50 patients with acute, subacute, and/or chronic cholecystitis with cystic duct obstruction proven histologically and operatively, and also to 27 non-diseased volunteers and 43 patients with right upper quadrant abdominal pain who subsequently were proven free of gallbladder disease. In addition, 38 patients had OC, and 31 had US performed. The results shows that the sensitivity and specificity of 99mTc-PGC were 100%. Whereas for OC the sensitivity was 87%, specificity was 100%. For US the sensitivity was 70%, and specificity was 93%. The repeatability of 99mTc-PGC, OC, and US were 100%, 97% and 81% respectively. These data show that 99mTc-pyridoxylideneglutamate cholescintigraphy is a valid diagnostic tool in the evaluation of patients with cholecystitis, and is also safe and simple.