Five current lines of cardiovascular studies in rats are outlined, mainly dealing with some functional and structural relationships of particular relevance for hypertension and ordinary aging: 1. Characteristics of the smooth muscles and their neurogenic control in 'Windkessel' arteries, conduit arteries, precapillary resistance vessels and venous capacitance vessels from normotensive rats (WKY) with comparisons to rats with primary hypertension (SHR). 2. Different types of structural renovascular adaptation, comparing aging with advancing SHR hypertension, with 'high-pressure' and 'low-pressure' kidneys in one-clip, two-kidney renal hypertension, and with hypertrophied kidneys in uni-nephrectomized normotensive rats. 3. Relationships between 'structural autoregulation', wall distensibility, vascular reactivity and smooth muscle sensitivity in SHR and WKY hindquarter resistance vessels along with aging. 4. Relationships between wall thickness, luminal dimension and contractility in left ventricles from SHR and WKY during aging, and when one-clip, two-kidney hypertension is superimposed. 5. Interference with the capacity of the neurohormonal mechanisms counteracting blood loss in rats when on chronic low-salt diet.