Summary—Simultaneous transmission and scanning electron microscopy studies were performed on lampbrush chromosomes ofNotophthalmus viridescensandXenopus laevis. The organization of their normal and landmark loop ribonucleoprotein (RNP) matrices was compared to that ofPleurodeles waltllampbrush loops, previously described. Ultrastructural observations clearly showed that in the three species, the RNP matrix of normal and landmark loops displayed a common basic structure: an RNP fibril packed into tightly juxtaposed RNP particles of remarkably uniform size,ie30 nm. Furthermore, analysis of the spatial arrangement of these constitutive RNP fibrils allowed us to establish ultrastructural similarities between the different types of loop matrices of the three species studied. Thus, granular loops with the same organization were found to be present in the three species, whereasPleurodeleswas the only one to exhibit, in its lampbrush chromosomes, the typical globular matrices previously described. “Sequential labelling loops” ofNotophthelmuswere shown to be similar of both “convoluted dense loops” ofXenopusand “dense loops”