AbstractThe reproducibility of complex protein patterns in two‐dimensional (2‐D) gels run with carrier ampholytes in the first dimension has been investigated. Two different laboratories collaborated in the study and 18 or 19 gels were run in each laboratory for comparison. The electrophoresis chemicals, running devices, and samples were standardized in both labs. The resulting 37 gels were scanned with a charge‐coupled device (CCD) camera and spots were located, counted, quantified, and matched using a commercially available image analysis system. Subsequently, the reproducibility of spot position was determined. To perform the statistical analysis, the test gels were initially each matched to a master references gel. Next, three sets of 12 gels (the image analysis software database could analyze only 12 gels at a time) were analyzed and the isoelectric point (pI) and molecular weight (Mr) positional variation of all the spots that matched across the gels in each set was determined. The resulting statistical analysis indicates very high reproducibility of the carrier ampholyte tech