Honeys with unique compositions and properties are worth studying for their health-promoting effects. In order to correlate bioactive content with immunostimulatory activity we compared the abilities of seventy eight New Zealand and non-New Zealand honeys to stimulate blood monocytes to release tumour necrosis factor (TNF)-a, and examined the compositions of selected honeys that had widely varying activities. All the honeys, except for a Malaysian ‘‘Amber honey” stimulated the release of TNF-a from monocytes. However, the honeys differed greatly in their immunostimulatory activity, even within the same honey type. They differed in their contents of immunostimulatory components, including apalbumins, arabinogalactan proteins, and apisimin, whose levels did not correlate exactly with immunostimulatory activities. We suggest that the immunostimulatory properties of honey may be influenced by other factors, including unidentified immunostimulatory bioactives and immunosuppressive components; the bioavailability of some bioactives may depend on unidentified factors.