The usefulness of CRP in early detection of neonatal septicemia/meningitis and urinary tract infection was studied in a neonatal unit using a semiquantitative latex-agglutination as a rapid screening method, and electroimmuno assay as reference method for CRP determination. In 94% of non-infected infants CRP was less than or equal to 15 mg/l and 82% had CRP less than 10 mg/l up to 3 days of age. After 3 days of age 96% had CRP less than 10 mg/l. The initial CRP level was increased in 16 out of 18 patients (89%) with bacterial septicemia. Low CRP was seen in one patient with total agranulocytosis and septicemia from Streptococcus type B and in one patient with Staphylococcus albus sepsis. A rise in CRP was also seen in very pre-term infants with septicemia. Increased initial CRP was uncommon in neonatal urinary tract infection (2 of 9), but a rise was seen in 3 additional patients. A comparison between CRP, total neutrophil blood cell count and band neutrophil count as diagnostic parameters was in favour of CRP at this early stage of infection. CRP is of definite value as an aid in early diagnosis of neonatal septicemia and bacterial meningitis.