Dispensing processes profoundly influence estimates of biological activity of compounds. In this study using published inhibitor data for the tyrosine kinase EphB4, we show that IC50 values obtained via disposable tip-based serial dilution and dispensing versus acoustic dispensing differ by orders of magnitude with no correlation or ranking of datasets. Importantly, the computed EphB4 pharmacophores derived from this data differ for each dataset. Acoustic dispensing correctly highlights multiple hydrophobic features in the pharmacophore and correlates with calculated LogP values. Significantly, the acoustic dispensing-derived pharmacophore correctly identified active compounds in a test set. The subsequent analysis of crystal structures for other published EphB4 inhibitors and automated development of pharmacophores, indicated they were comparable to those developed with acoustic dispensing data. In short, dispensing processes are another important source of error in high-throughput screening that impacts computational and statistical analyses. These findings have far-reaching implications in biological research and in drug discovery.