Following the publication of the history and development of QSAR, it became apparent that a number of matters had not been covered. This addendum is an attempt to rectify that. A very early approach (ca. 60 B.C.) by Lucretius shows that he understood how molecular size and complexity affect liquid viscosity. Comments by Kant (1724-1804) emphasized the necessity of mathematics in science. A claim that the work of von Bibra and Harless in 1847 pre-dated that of Overton and H.H. Meyer is shown not to be correct. K.H. Meyer and Gottlieb-Billroth published in 1920 what is probably the first QSAR equation. Brown, who with his co-author Fraser is credited with the first definitive recognition in 1868-9 that biological activity is a function of molecular structure, is often cited as Crum Brown; in fact, Crum was his second given name. The QSAR work of the Soviet chemist N.V. Lazarev in the 1940s was far ahead of his time, showing numerous correlations of biological activities and physicochemical properties with molecular descriptors. The subject of inverse QSAR is discussed.