Net photosynthetic rate (A_n), stomatal conductance (g_s), intercellular CO₂ concentration (C_i), and chlorophyll concentration estimate ([Chl]) were measured on flag leaves of 30 random individual F₅ plants within each of eight F₂-derived bulks, from a cross between two spring wheat (Triticumaestivum L.) cultivars, Seri-M82, and Siete Cerros-T66 contrasting in A_n, and realized grain yield. Measurements were made on fully irradiated leaves of field plots growing in a warm, low relative humidity, irrigated environment. Average A_n of F₂-derived families measured during grain filling ranged from 19.1 to 24.4μmolm⁻²s⁻¹ among families, with standard errors ranging from 0.35 to 0.53. Based on measurements of A_n of flag leaf lamina of individual plants, measured several times during grain filling, four plants from each of four bulks were selected for high and low A_n to represent the range of genetic diversity within and among F_2:5 families. From each of these 16 selected F₅ plants, head rows were grown to generate inbred F_5:7 lines for replicated yield trials, which were sown in two environments in the same locality, differing by five weeks in sowing date, and having mean grain yields of approximately 3.5tha⁻¹. Mean A_n measured on randomly selected flag leaves of the inbred lines ranged from 16.3 to 24.6μmolm⁻²s⁻¹ over both sowing dates. A_n, g_s, and C_i all correlated with yield of inbred lines. Furthermore, A_n and g_s measured on individual F₅ plants correlated genetically and phenotypically with A_n, g_s, and yield of the inbred lines deriving from the same plants, in both environments where yield was evaluated.