Malyngamides D and E are two trans-7-methoxy-9-methylhexadec-4-enamides that have been isolated from the lipid extract of a deep water variety of the marine blue-green alga Lyngbya majuscula. Detailed spectral analysis, mostly NMR, and chemical degradation show that malyngamides D and E have the gross structures 2 and 3, respectively. Malyngamides D and E produce the same diacetate on acetylation. The ring stereochemistry of 2 and 3 has been defined from NMR and chemical reactivity data.