PDLAQR1: An improved version of the ScaLAPACK routine PDLAHQR. PDLAQR1 is a modified version of ScaLAPACK (version 1.8.0) routine PDLAHQR. In this note we summarize the difference between these routines. Some anomalies in the old routine are identi ed and xed. We also implement some new features such as aggressive early de ation to improve the performance. The new routine is both faster and more reliable than the old one.