To evaluate the value of C-reactive protein and leukocyte indices in the workup of patients suspected of having infection in a neonatal intensive care setting, a literature search was conducted in all languages using MEDLINE (1966 to May, 1994), EMBASE (1988 to May, 1994), bibliographic lists of primary and review articles and personal files. Citations identified as potentially relevant were reviewed by two independent investigators; only studies meeting preset criteria for population, diagnostic test and data presentation were included. Two observers independently assessed studies using explicit methodologic criteria. All data from the articles were extracted by one observer, whereas the second reviewer checked these data for accuracy. Four of the selected studies dealt with leukocyte count and ratios. The chi square test for homogeneity of proportions revealed significant heterogeneity across studies (P = 0.014 for the ratios; P < 0.001 for white blood cell count), suggesting that test properties varied widely across studies. Fifteen of the selected studies evaluated C-reactive protein; of these six were qualitative using a latex agglutination method. Among these studies the chi square test for homogeneity of proportions was highly significant (P < 0.01), reflecting the great heterogeneity across studies. Among the nine studies that evaluated five different quantitative methods heterogeneity was again present (P < 0.001). Because of the striking heterogeneity among the studies evaluated, pooling to give a summary point estimate of the sensitivity and specificity of the various studies was not possible and the results are reported as ranges.(ABSTRACT TRUNCATED AT 250 WORDS)