Whatinfluence occupation hasuponarterial pressureisuncertain. Ischaemic heart disease isknown tobemorecommonamongmeninsedentary thanin heavy occupations (Morris, Heady, Raffle, Roberts, andParks, 1953; Brown, Davidson, McKeown, and Whitfield, 1957; Morris andCrawford, 1958) and there isgoodevidence that theattack rateincreases withincreasing arterial pressure (Brownandothers, 1957). Onewouldexpect tofind, therefore, that men insedentary occupations tendtohavehigher pressures thanmendoing heavy work. Theresults ofa survey carried outbyMiall andOldham(1958) in South Walesappear tobeinline withthis expectation-men doing light workwerereported tohave hadsomewhat higher pressures thanthosedoing heavy work.Butastudy byEdwards, McKeown, andWhitfield (1959) inBirmingham produced results which suggested theopposite ofthis. Arterial pressure wasmeasured in1,723 representative men overtheageof60andwasfound tobealittle higher inSocial Classes IVandV (semi-skilled andunskilled occupations) thaninClasses I andII (professional andintermediate occupations). Noexplanation hasbeenoffered forthedifference between thefindings inSouthWalesandBirmingham,andnational dataonoccupational mortality dolittle toclarify theposition (Registrar General, 1954). Fortheyears 1949-53, mortality attributed to tohypertension amongmenaged20-64 appeared to follow thesamepattern asmortality attributed to coronary disease, andtended todecrease, although notsosteeply, fromSocial Class ItoV.Ontheface ofitthis appears tosupport thefindings inSouth Wales. TheRegistrar General warns, however, that trends inthesocial class mortality ofmenaged20-64 mustbeinterpreted withcaution, forwhenthe statements ofoccupation on10,000 death certificates issued 3weeksafter thecensus werecompared with thestatements intherelated censusschedules, a tendency toupgrade social class on thedeath certificate wasdisclosed whichwouldhavebeen sufficient toincrease theapparent mortality for Classes IandIIbyperhaps asmuchas25percent.