In this study the impact of the Dutch dietary guidelines diet on various health status parameters was examined. Twelve apparently healthy men aged 35-52 years were given both the guidelines diet (G) and the 'average' Dutch diet (D) in a controlled eight-week study period with a cross-over design. Compared with the D diet, the G diet contained less fat (accounting for 35 per cent vs 44 per cent of total energy intake), about half the amounts of saturated and monounsaturated fatty acids and twice the amount of polyunsaturated fatty acids. The G diet was given either as a high-sugar or as a low-sugar variant (25 per cent and 15 per cent of total daily energy intake, respectively). Serum total, LDL- and HDL-cholesterol decreased during the four-week G diet from 5.76 to 4.99, from 3.95 to 3.35 and from 1.13 to 1.03 mmol/l respectively. Also the apo-lipoprotein A-I, A-II and B concentrations decreased in subjects on the G diet. Blood pressure and body composition did not change significantly. Urinary pH and the excretion of sodium and potassium were significantly lower for the G diet. It is concluded that the combined factors in the Dutch guidelines diet, irrespective of amount of sugar, has favourable effects on total and LDL-cholesterol levels, whereas the decrease of the concentrations of HDL-cholesterol and of apo-A-I and A-II is less desirable. The changes in urinary mineral excretion, in particular of sodium, during the G-diet is considered as a positive effect.