Covering: 1980 to end 2014A diverse range of strategies leading to natural product derived or inspired screening libraries aims to increase the number of new chemical entities emerging per year. However, the use of isolated natural products as scaffolds for the semi-synthesis of larger biological screening libraries remains rare. This particular method avoids the time-consuming and resource intensive de novo synthetic strategy for scaffold production, and has become more feasible through improvements to synthetic and isolation methodologies. This Highlight examines the increasing popularity of small- to large-sized screening libraries generated directly from isolated natural products. Several of the examples detailed herein show how this strategy can lead to improvements in not only potency but also other important (and often forgotten) drug discovery parameters such as toxicity, selectivity, lipophilicity and bioavailability. However, there are still improvements to be made to this method, particularly in the choice of the natural product scaffold and the derivatising reagents used. Avoidance of known nuisance compounds or structural alert motifs (e.g. PAINS) that interfere with bioactivity screens, and impact downstream drug development will play a significant role in the future success of this methodology. Incorporation of rational design strategies that take into account the physicochemical parameters (e.g. log P, MW, HBA, HBD) of the final semi-synthetic library analogues will also facilitate the discovery and development of leads and drugs. A multi-pronged approach to drug discovery that incorporates the use of isolated natural product scaffolds for library generation will surely be beneficial.