Cytoplasmic hepatitis B virus (HBV) capsids are not enveloped and secreted unless the packaged RNA pregenome is reverse transcribed. The expression of the capsid protein C, together with envelope proteins in the absence of pregenomic RNA, produced normal amounts of intracellular capsids, but the secretion of virion-like particles was greatly reduced. The I97L C protein mutant, allowing immature nucleocapsid envelopment in the background of an HBV genome, did not promote the envelopment of capsids lacking a pregenome, suggesting that this mutation is not sufficient to induce secretion competence independently of the pregenome.