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Protoplast-to-plant systems for the Egyptian medicinal plants Artemisia judaica L. and Echinops spinosissimus Turra have been developed. Micropropagated shoots of A. judaica and E spinosissimus were selected as plant materials suitable for protoplast isolation. The yield and viability of protoplasts in both species were greatly influenced by osmotic potential and enzyme combinations. Sustained cell division and colony formation from the protoplasts of A. Judaica were best supported by a medium containing 0.6 mol l(-1) glucose, 2.5 mumol l(-1) 6-benzylaminopurine (BAP) and 5.0 mumol l(-1) 1-naphthaleneacctic acid (NAA) in 0.6% Agarose (SeaPrep(R)) block/liquid culture. The highest frequency of colony formation in E spinosissimus was observed when the protoplasts were embedded in 0.6% Na-alginate block and cultured in a medium containing 1/2 strength Murashige and Skoog, 1962 (MS salts), Gamborg et al., 1968 (135 vitamin), 0.5 mol l(-1) glucose, 2.5 mumol l(-1) BAP and 5.0 mumol l(-1) 2,4-dichlorophenoxyacetic acid (2,4-D). The protoplast-derived colonies formed green compact calli when transferred onto 0.25% gellan gum-solidified MSO medium supplemented with 2.5 mumol l(-1) BAP and 2.5 mumol l(-1) NAA for A. judaica, and 2.5 mumol l(-1) BAP and 2.5 mumol l(-1) 2,4-D for E. spinosissimus. Shoot organogenesis from the protoplast-derived callus was induced on MS medium supplemented with 5.0 mumol l(-1) BAP for A. judaica and 2.5 mumol l(-1) BAP for E spinosissimus. The protoplast to plant regeneration protocols developed in this Study may provide the basis to investigate cell physiology and biochemistry of desert medicinal plants. (C) 2003 Elsevier Ireland Ltd. All rights reserved.