<jats:title>Abstract</jats:title><jats:p>Tricladins A and B (<jats:bold>1</jats:bold> and <jats:bold>2</jats:bold>, resp.), new imidazolone‐containing alkaloids, together with five known metabolites, bacillamides A, B (<jats:bold>3</jats:bold> and <jats:bold>4</jats:bold>, resp.), 20‐hydroxyaflavinine (<jats:bold>5</jats:bold>), <jats:italic>N</jats:italic>‐(2‐phenylethyl)acetamide (<jats:bold>6</jats:bold>), and <jats:italic>N</jats:italic><jats:sub>b</jats:sub>‐acetyltryptamine (<jats:bold>7</jats:bold>), have been isolated from the crude extract of the ascomycete fungus <jats:italic>Tricladium</jats:italic> sp. The structures of <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold> were elucidated primarily by NMR and MS methods. Compound <jats:bold>2</jats:bold> showed marginal cytotoxicity against MDA‐MB‐231 human breast cancer cells, whereas the known metabolite <jats:bold>4</jats:bold> displayed an inhibitory effect on HIV‐1 replication in C8166 cells.