There are several downhole parameters and events, such as weight and torque variations, stick-slip and whirl affecting drill bit performance. These phenomena have been studied and reported in industry literature in recent years. The evolution of downhole mechanics measuring tools has allowed continued progress in the understanding of bit and drillstring dynamics. Field tests have been performed with downhole tools developed to investigate the performance of drill bits and BHA components. Case studies of these measurements will be presented including downhole measurements of bit whirl and stick-slip.