Differences in pea root length, root surface area, and diameter were rapidly determined using the WinRhizo computer program. Repeatable differences were measured both in the laboratory and in the field. Large-rooted lines, as measured in the laboratory, also were the largest-rooted lines in the field. Large-rooted lines produced more roots and had more root surface area when exposed to a 1.6 g cm-3 bulk density compacted layer with the presence of the Fusarium root rot pathogen (Fusarium solani f. sp. pisi). Also, large-rooted lines regenerated more roots when one-third or two-thirds of the root system was removed or when one cotyledon was removed from 5-day-old plants. Large-rooted pea lines should have an advantage in growing under adverse conditions of compaction and the presence of Fusarium root rot.