A detailed analysis of the secondary metabolites of the sponge Pseudoceratina crassa has been performed. The structures of a new sterol (7) and four new bromotyrosine derivatives (8-11) were determined by spectroscopic analysis. The bromocompounds of P. crassa can be used as chemical markers to support the identification of the sponge based on morphological characters. Verongida (Bergquist, 1978) are marine sponges chemically characterized by a series of secondary brominated metabolites, biogenetically arising from bromotyrosines, none of which are yet known to occur in any other marine sponge. In comparison with the extensive chemical investigation on these organisms, which led to the isolation of more than one hundred novel bromocompounds, uncertainties exist concerning the identification of the species which these products derive from. The difficulties in identifying the species belonging to this order come from their high phenotypic variability and from the absence of reliable skeletal characteristics. In addition, a systematic revision of the Caribbean Verongida is still lacking and is highly needed. Some discrepancies can be noticed by examining the data reported on the constituents of Pseudoceratina crassa, a Verongida species which has been reported in the sponge literature also under different names, such as Aiolochroia crassa (Hyatt, 1875), Ianthella ianthella (De Laubenfels, 1949), Ianthella ardis (De Laubenfels, 1950) that are considered as synonyms. In 1981 Makarieva & al. report aeroplysinin-1 (1), aeroplysinin-2 (2) and 2-(3,5-dibromo-4-ethoxy-1-hydroxy-4-methoxy-2,5-cyclohexadien-1-yl) ethanamide (3) as the major compounds of a specimen of Aiolochroia crassa, collected along the Cuban coast. In 1986 a sample of Ianthella ardis (Bahamas) was shown to elaborate large quantities of ianthellin (4, 1.4% dry weight), and smaller amounts of aeroplysinin-1 (1, 0.01% dry weight) by Litaudon and Guyot, but no mention about the co-occurrence of compounds 2 and 3 was reported. Finally in 1991 Kassuhlke and Faulkner by studying a Caribbean sample of P. crassa, collected near Albert Town (Bahamas), observed a single UV-absorbing spot in the organic extract. This material was isolated and identified as ethyl 3,5-dibromo-(3'-N,N-dimethylamino-propyloxy) cinnamate (5, 0.13% dry weight). Additional quantities of the free acid (6, 0.2% dry weight), were recovered from the aqueous extract. During the Fenical expedition in July 1990, along the coasts of the Bahama Islands, we collected several specimens of the same sponge species which was identified on the basis of the external morphology (colour, oscules, conules, consistency etc.), observed and photographed in vivo, and the peculiar characteristics (few, brittle fibers, more than 500 μm thick, rarely forming meshes) of the skeleton. We can reasonably suppose that our specimens - which perfectly match with the recent descriptions of Wiedenmayer (1977) and Van Soest (1978) - are conspecific with those studied by some of the authors cited before. To gain a detailed knowledge on the secondary metabolism of this sponge, which could be usefully utilized to attain unambiguous identification of P. crassa species, our Caribbean specimen has been extensively analyzed. In this paper we report the obtained results. A number of secondary metabolites (1, 4, 7, 8-11, 12) have been isolated and quantified. Compounds 1 and 4 are known compounds previously isolated from Verongida sponges. The isolation from the same P. crassa sample of the six five-membered cyclitol glycolipids (12) and their structure determination are reported in a recent paper of our research group. The present communication describes the structure elucidation of the novel compounds 7-11.