Variation in stem diameter and other stem attributes of wheat in relation to yield components were analyzed in a 7- parent F₁ diallel cross in favorable, drought and combined drought heat environments. In addition 12 F₂ populations were also tested  under heat stress. Polygenes with mainly additive effects were involved in the control of stem diameter which segregated in normal distributions in the F₂. The narrow-sense heritability was of comparable magnitude under favorable (0.73); drought (0.62) and drought + heat stress (0.76).  Whereas, heritability of stem dry weight was reduced under stress. Non-allelic duplicate interaction was operating for stem density under drought stress. Stem diameter was positively correlated under both drought and drought + heat stresses with stem weight and stem density. Stem diameter was significantly associated with 1000 kernel weight and grain yield per spike in the three environments. On he other hand stem density was only associated with single grain mass under favorable condition and with grain yield per spike under drought stress only. Such strong associations of stem diameter with single grain mass and grain yield per spike under stress indicated the importance of this character which plays a role in sustaining grain filling through providing greater capacity of storing assimilates in the stem before mobilizing it to grains.