To study the impact of the professional background of infection control personnel, we compared the characteristics and activities of 107 infection control nurses (ICNs) with those of 13 infection control laboratorians (ICLs), all in hospitals with 300 beds or more. Although the two groups performed similarly in many respects. ICNs spent more time teaching, whereas ICLs spent more time and appeared more proficient in investigating outbreaks. Staff nurses at hospitals with ICNs found the infection control person more visible on the wards and more available for discussing infection control matters. ICNs appeared less hesitant to speak up to personnel not following correct handwashing techniques. ICNs and ICLs appear to offer different skills that should be considered when filling different infection control positions.