Polyclonal and monoclonal antibodies to platelet-activating factor (PAF) were produced, by use of colloidal gold as the hapten carrier. These polyclonal (R88-09) and monoclonal (602 B11) antibodies both reacted with PAF, lysoplatelet-activating factor (lyso PAF), and L-α-lysophosphatidylcholine, palmitoyl (lyso PCP), but did not react with phosphorylcholine chloride (PCC) . Their affinities were higher for PAF than lyso PAF and lyso PCP.