Protein content was determined by a modified biuret method for 10 field pea cultivars grown for 3 yr at a single location and for 19 cultivars grown for 1 yr at four locations. Significant differences were found among cultivars, locations, and years. Cultivar × location interactions were also significant. The average protein content among cultivars varied from 23.1 to 28.3%, among locations from 24.0 to 26.3%, and among years from 25.8 to 27.4%. Differences in protein content at three positions on single plants were also determined, but were not large. Protein content of individual plants within cultivars varied significantly. Correlations between protein content and yield, maturity, or seed size were not significant. A range of 22–32% protein was found among 506 plant introductions.