MLL supplemental files include the following: 1. Scan id file (tab-delimited text). This file contains link between sample names, scan names, and scaling factors. 2. Processed Expression data files (2 tab-delimited text files). Each file contain scaled Affymetrix "average difference" expression values for all samples. Expression values are identical in the two files, but the second file also includes Affymetrix "Present" (P) and "Absent" (A) calls. Linear scaling was used to reduce technical noise due to global intensity differences between scans. Linear regression of all "Present" genes (Affymetrix "P" calls) was used to determine the scaling factor for each scan (the first ALL scan used as a reference). The scaling factor was applied to expression values (regardless of A/P call). Scaling factors ranged from 0.93 to 2.1; all scaling factors are shown in scan id file. Data files include expression values for 12582 probe sets from the Affymetrix U95A chip. Excluded are 25 probe sets determined by Affymetrix to be erroneous. Data for 18 "spiked" (exogenous) controls were also excluded, as these hybridization controls were added to only a subset of samples. 3. Raw "CEL" files which contain fluorescence intensities for all probes on chip. These files are zipped tar archives. Each file contains data for 10-14 scans.