Pattern analysis, cluster and ordination techniques were applied to grain yield data of 24 cultivars of 2- and 6-rowed barley (Hordeum vulgare L.) grown in 26 environments in Turkey during 2004-2008 to identify patterns of genotype (G), environment (E) and genotype x environment interaction (GEI) in barley multi-environment trials (METs). Analysis of variance showed that 86.9% of the total sum of squares was accounted for by E. Of the remaining sum of squares, the contribution of GEI was almost 9 times that of the contribution of G alone. Knowledge of environmental and cultivar classification helped to reveal several patterns of GEI. This was verified by ordination analysis of the GEI matrix. Grouping environments based on cultivar performance resulted in the separation of different types of environments. Pattern analysis confirmed 2 mega-environments in the highest similarity level and allowed the discrimination and characterization of barley cultivar adaptation. The high-yielding environments (Eskisehir and Konya; first mega-environment) tended to be closer to one another, suggesting that they discriminate among barley cultivars similarly, whereas low-yielding environments tended to be more diverse (Afyon and Usak; second mega-environment). Cultivars with similar patterns in performance were separated into 5 clusters. The two 6-rowed (Kiral-97 and Cetin-00) and two 2-rowed barley cultivars (Sahin-91 and Aydan hanim) with low to medium yields (3.60-3.84 t ha(-1)) contributed greatly to GEL and were highly adapted to high-yielding environments. The tall and later maturing 2-rowed barley cultivars (Karatay-94, Ince-04, Kalayci-97, Ozdemir-05, Tokak 157/37, and Keser) with high yields (4.35-4.18 t ha(-1)) were highly adapted to most of the environments studied.