Variation in both the total content and the concentration of glycinebetaine in response to increasing soil salinity was studied in the salt‐secreting Atriplex griffithii Moq., the leaf succulent Suaeda fruticosa (L.) Forssk., the stem succulent Haloxylon recurvum Bunge ex Boiss. and the osmotically adjusting desert grass Halopyrum mucronatum (L.) Stapf. collected from a subtropical maritime desert in Pakistan. Glycinebetaine content (mmol kg−1 dry weight) increased with increasing NaCl in Atriplex griffithii, Haloxylon recurvum and Halopyrum mucronatum, but peaked at 600 mM NaCl for Suaeda fruticosa and declined thereafter. Glycinebetaine concentration (mmol l−1 tissue water) increased with increasing salinity in all four halophyte species and was sufficiently high to serve as an osmoticum in all cases.