To compare rates of ischaemic heart disease (IHD) among men in occupation groups defined by the new Australian Standard Classification of Occupations (ASCO) and to investigate whether their high mortality rates from IHD in the Hunter Region of New South Wales (NSW) could be explained by its occupational structure, we used official death records and data from the World Health Organization MONICA Project conducted in Newcastle. The study population consisted of men aged 25 to 64 years in NSW and in the Hunter Region for whom occupational information was available. For deaths from IHD between 1984 and 1988 in NSW, indirectly standardised mortality and morbidity ratios (SMRs) were: significantly low for professionals, 66 (95% confidence interval (CI) 60-71) and managers and administrators, 79 (95% CI 74-83); intermediate for paraprofessionals (92), clerks (94) and salesmen and personal service workers (97); and significantly high for tradesmen, 113 (95% CI 107-118), labourers and related workers, 118 (95% CI 113-124) and plant and machine operators and drivers, 125 (95% CI 118-133). Broadly similar patterns were found for IHD deaths and for fatal and nonfatal myocardial infarction in the Hunter Region. When occupation- and age-specific mortality rates from IHD were used to calculate SMRs for the Hunter Region, SMRs for all ASCO groups except paraprofessionals were over 100. Mortality rates for occupational groups classified by ASCO were consistent with well-established differences associated with socioeconomic status.(ABSTRACT TRUNCATED AT 250 WORDS)