Background: Progressive loss of kidney function results in an increased risk of malnutrition. Despite this, there is little evidence informing the impact of nutrition intervention on predialysis patients with chronic kidney disease (CKD; stages 4 and 5). Study Design: Randomized controlled trial. Setting & Participants: 56 outpatients (men, 62%; mean age, 70.7 ± 14.0 [SD] years) with CKD were randomly allocated to intervention (n = 29) or control (n = 27) by using a concealed computer-generated sequence. Intervention: The intervention group, provided with individualized dietary counseling with regular follow-up aimed at achieving an intake of 0.8 to 1.0 g/kg of protein and greater than 125 kJ/kg of energy, or control, receiving written material only. Outcomes & Measures: Change in body composition (body cell mass, measured by means of total-body potassium, in 40 of 56 participants), nutritional status (Subjective Global Assessment), and energy and protein intake (3-day food record). Results: During the 12 weeks, the intervention group had 3.5% (95% confidence interval, -2.1 to 9.1) less decrease in body cell mass, 17.7-kJ/kg/d (95% confidence interval, 8.2 to 27.2) greater increase in energy intake, greater improvement in Subjective Global Assessment (P < 0.01), and no significant difference in protein intake compared with the control group (-0.04 g/kg/d; 95% confidence interval, -0.73 to 0.16). The intervention was associated with greater increases in energy and protein intake in women than men (interaction P < 0.001 for both). Limitations: Power to detect change in body cell mass, potential bias in ascertainment of Subjective Global Assessment. Conclusions: In predialysis patients with CKD, structured nutrition intervention had a greater effect on energy and protein intake in women than men. Additional investigations are warranted to determine the impact on body composition.