Assay-ready compound plates (ARPs) are sealed assay plates that contain DMSO solutions of screening compounds predispensed for particular assays. Assays are started by adding assay buffer and reagents to the ARPs. This concept offers important logistical advantages for screening such as decoupling of the plate preparation from the screening process and exchange of assay plates between different geographical locations. Compound solutions can be accurately and precisely dispensed by acoustic droplet ejection technology in the small volumes required for screening in the 1536-well format. At such low volumes, however, potential effects such as solvent evaporation, compound degradation, precipitation, or adsorption are reasons for concern with regard to assay reproducibility, performance, and shelf life of ARPs. To address these concerns, the authors screened freshly prepared ARPs using several types of assays. The results were compared to results obtained from plates stored for up to 13 days under 2 storage conditions (22 degrees C, -18 degrees C). Tight correlations between results were found that indicated that temperature and time had very little influence on the assay performance for up to about 1 week storage time of the plates. In addition, using a time series of microphotographs of DMSO droplets, the authors visually confirmed that the sizes of the droplets in ARPs apparently do not change over 13 days under certain storage conditions.