It is widely believed that the Green Revolution had very little effect in unfavourable or marginal environments. Many researchers have been concerned about the slow progress of technical change in marginal environments and the level of research resources allocated to these areas. This paper provides empirical evidence that there has been significant growth in wheat yield potential in marginal environments, especially during the post-Green Revolution. International yield trial data, covering all major wheat growing environments from 1964 to 1999, were used in estimating the growth in wheat yield potential and changes in yield variability. The global database on wheat varietal adoption and yield gains based on estimated wheat yield growth rates were used to determine production increases due to wheat breeding research. Results show greater progress in shifting the wheat yield frontier in marginal areas, particularly in drought and high temperature environments. Furthermore, yield variability in marginal environments has notably declined, while it has increased slightly in favourable environments. While initial gains came from crossover of varieties from favourable environments, targeted breeding efforts have contributed significantly to more recent productivity growth in marginal environments. Increased production from marginal environments accounted for around 25% of the total wheat production increase in 1997. These findings show greater progress in wheat research and the huge potential of improving wheat productivity in unfavourable environments. © 2003 Elsevier B.V. All rights reserved.