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The Umm Az Zimul-Al Wijan area is located in the southeastern part of the UAE and covers about 1600 km(2). It is bounded to the east by the Oman Mountains and to the south and west by the extensive dune area of,Ar Rub Al Khali. Field investigation revealed the common occurrence of parallel to sub-parallel sand ridges with a general east-west orientation. Also present, but less frequent, are barchan, barchanoid and star dunes. Interdune areas are classified into four types that include: dolomite, mixed ancient sabkha and ophiolitic rock fragments, mixed sand sheet and ophiolitic rock fragments, and recent sabkha. The textural characteristics of the sand forming the dunes are unimodal with a modal class in fine sand size, moderately to very well sorted, positively skewed and mesokurtic. Quartz grains are mainly subrounded to subangular. The similarity in roundness properties in different dune types in the eastern province of the UAE seems not to be influenced by dune form. Based on the heavy mineral suites and the angularity of quartz grains, it is believed that the sand sediments are mostly derived from the ultrabasic rocks forming the ophiolitic sequence of the Oman Mountains, acidic rocks of Iran and from the coastal area. (C) 1999 Elsevier Science B.V. All rights reserved.