Technical Abstract: Uniformity of plant responses and gas exchange calculations within and among Soil-Plant-Atmosphere-Research (SPAR) chambers was evaluated using 12 SPAR chambers located at Beltsville, MD. Periodic non-destructive and destructive measurements were conducted at the same locations within each chamber using wheat (Triticum aestivum L. cv. USU-Apogee) as the crop. Identical experimental protocols were applied to each chamber. Analysis of variance indicated significant locational effects within chambers at three different harvest dates. The patterning of variation within the SPAR chambers was primarily South to North and largely a response to radiation gradients, wind speed, and soil media settling. No significant differences among final chamber means for any plant response were found, and most values were within 95% confidence limits of the pooled chamber mean. Analysis of canopy radiation interception and photosynthetic responses indicated that differences among chambers were due to variation in establishment of leaf area. This variation was attributed primarily to differences in emergence rate, irrigation delivery, and media settling. Overall, this study indicated that, when appropriate, experimental protocols are followed and within-chamber positional effects are taken into account during sampling. Differences among chambers for plant responses are due to experimental treatment and not inherent differences in chamber performance.