The egg of Trichoprosopon compressum is described and illustrated from material collected in the vicinity of Sao Paulo, Brazil. The egg is divided longitudinally into non-wettable (dorsal) and wettable (lateral and ventral) surfaces, which differ markedly in structure. On the dorsal, hydrofuge surface, the chorionic cells around the central mid-line contain ridges loosely aligned in the long axis, or in some eggs more organized into two continuous lines. About one-third of the dorsal width of the egg from the central line the chorion is folded on each side into two very prominent longitudinal ridges, which join anteriorly and posteriorly. Around the dorsal margins of the egg are closely spaced, flap-like outgrowths. The ventral, wettable surface is covered uniformly with cells containing broad, flat spatulate tubercles almost invariably with one or more surface furrows positioned near the mid-line. The tubercles increase progressively in size from the lateral to mid-ventral regions of the egg, except for approximately the anterior and posterior one-sixth.