We report six cases of possible acute cardiovascular death in young adults, where very recent cannabis ingestion was documented by the presence of tetrahydrocannabinol (THC) in postmortem blood samples. A broad toxicological blood analysis could not reveal other drugs. Similar cases have been reported in the literature, but the toxicological analysis has been absent or limited to urine samples, which represent a much broader time window for cannabis intake. This paper presents six case reports, where cannabis alone was detected in blood. Further, an overview over previously published cases, clinical trials and possible patho-physiological mechanisms are presented.