Summary: Monocyte and polymorphonuelear ncutrophil (PMN) cheinotaxis was studied in cord blood from healthy term infants. Monocyte chemotaxis was normal to increased (115–126%) whereas PMN chemotaxis was decreased (79%) in comparison with that of healthy adult control subjects. Generation of chemotactic factors from cord sera was impaired, being 55% of that generated by pooled normal human serum (PNHS). Cord serum was less inhibitory than pooled adult human serum for adult monocytes when the cells were suspended in 10% scrum and tested for chemotaxis. No inhibition of chemotactic factors by cither cord or adult sera was observed. The dissociation of chemotactic response of the two different phagocytic cells may represent a protective mechanism whereby one cell can compensate for a defect in the response of the other. Speculation: Simultaneous analysis of monocyte and ncutrophil chemotaxis may reveal a defect restricted to one cell type.