A field study was conducted on a fog-dependent vegetation zone, near the coast, on the deseitic regions northof Chile; 3 different valleys were sampled: Paposo, Taltal and Cifuncho (23° 25’ Lat. S; 70° 30’ Long. W).Microarthropods were sampled under 16 plant species and on soil without vegetation. Sampling wasrepeated on 6 different dates, along 1993, 1994 and 1995.Results, based on the study of 233 soil samples, treated by means of Berlese-Tullgren funnels, show atypical microarthropod composition, with 26 supraspecific taxa, among which the dominant ones areProstigmatid and Cryptostigmatid mites, and Psocopteran insects; this for xerophytic conditions; in adifferent hydrophytic situation other taxonomic structure was found, where Collembola and insect larvaewere the dominant ones.Data on sample frequency (%) and mean densities are given for each taxon and plant species. Workingwith these most frequent taxa, Kruskal-Wallis tests show for Oribatids, Prostigmatids, Psocoptera and alsothe total fauna, very significant differences in their abundances, depending on the plant species factor.Otherwise, one-way analysis of variance on the above cited most frequent taxa show that the sample datefactor was significant in 5 cases for Oribatids, in 3 cases for Prostigmatids and in 4 cases for Psocopterans;all three taxa show significant sampling time variations under Nolana ciivata and Dinemandra ericoides; only2 of them vary significantly under G ypotham nium pinifolium and Eulychnia breviflora; also, only Psocopteravaried significantly under Lycium fra g o su m and in bare soils.Another two-way analysis of variance, shows no significance for either factor (valley; sampling date) withdata from Oribatid mites, Psocoptera or Total fauna. Prostigmatid mites, on the contrary, shows significancefor both factors but no for interaction.