The objective of the study was to determine the relationship between exercise systolic blood pressure (ESBP), during bicycle ergometry, and echocardiographically determined left ventricular structure in rural and urban Canadian men of Icelandic descent. The study was cross-sectional in design. The settings were urban Winnipeg and the rural Interlake District in the province of Manitoba, Canada. Subjects were adult male volunteers from families of wholly Icelandic descent. The subjects were 30 to 60 years of age and had supine blood pressure or = 200 mm Hg) and left ventricular hypertrophy (LVH) was not significantly different in the two groups. In all but one individual LVH was classified as eccentric hypertrophy. In both urban and rural subjects with exaggerated ESBP, left ventricular mass index (LVMI) was greater than in those subjects without exaggerated ESBP. The LVMI correlated with ESBP at the highest workloads (> or = 150 W). Multivariate analysis of all subjects showed that cardiac index, ESBP, body mass index, and low exercise heart rate were predictive of LVMI. There was no significant difference in prevalence of ESBP or LVH between urban and rural Manitobans of Icelandic descent. However, LVMI levels were lower, and values for ESBP greater, in the rural group compared with the urban group. Within each of the two groups there was a positive association between ESBP and LVMI; hence, the study supports findings of our previous investigation showing evidence of early target organ effects in normotensive men with an exaggerated ESBP.