The University of Washington together with the ISDS has undertaken a comprehensive analysis of the quality of the data being received by Distribute, primarily using visual methods, examining data quality characteristics within and between sites. Several visualization tools were developed to assist in analyzing and characterizing data quality patterns for each site: upload pattern graphs (Fig. 1) , stacked lag histograms and arrays of lagged time series graphs. Upload pattern graphs are heat maps comparing upload dates with encounter dates (an example figure is given below for three sites). Stacked lag histograms provide a succinct view of the complete distribution of data timeliness for a particular site. Arrays of lagged time series graphs provide an in-depth look at how timeliness patterns manifest in time series graphs. Implementation of the latter two visualizations required implementing a specific database architecture to enable reconstruction of the data at any prior upload date.