The jellifying capacity of some alginate gels excreted by Azotobacter vinelandii DSM 576 was studied by oscillatory tests at alginate concentrations (c) of 1.0% and 1.5% w/w. Frequency dependence of the complex shear modulus (G*) permitted these gels to be discriminated in terms of their different orders of the relaxation function (alpha) and "gel stiffness" (A(alpha)) values using Friedrich and Heymann theory [Journal of Rheology, 32 (1988) 235]. Of the samples tested that characterised by a guluronate content of 25% and a number-average molecular mass (M-n) of 263.4 kDa exhibited a gel stiffness at c = 1% w/w of the same order of magnitude of that pertaining to alginates extracted from Macrocystis pyrifera or Lessonia nigrescens with greater guluronate contents (35-40%) but smaller number-average molecular masses (70-110 kDa) with about half of alpha. Whereas alpha was found to depend exponentially on the ratio of guluronate to mannuronate monad frequencies (N-G/(M)) only, A(x) was expressed as a power function of c, M-n N-G/M, and average G-block length (N-G). The limited data available, as well as incomplete understanding of the real controlling factors for ionotropic gelation of alginates, made such empirical correlations just useful for a preliminary screening of alginates independently of their weed or microbial origin. (C) 2003 Elsevier Ltd. All rights reserved.