A simple and non-radioactive technique based on O-cresolpthalein complexone assay was developed to study in vitro non-radioactive calcium ((40)Ca) deposition by isolated matrix vesicles. Using this technique, the effect of various phosphoester substrates including ATP, AMP and beta-GP on in vitro MV-calcification was studied. O-cresolpthalein complexone assay with non-radioactive calcium demonstrated that AMP or beta-GP were more effective in promoting calcium deposition by isolated MVs than ATP. The application of this non-radioactive technique, which is highly sensitive and simple, would offer a useful alternative approach to the routinely used radiometric biomineralization assay which employs radioactive (45)Ca.