The potential for vector-independent transmission of pathogens to occur in what is generally considered to be a vector-borne system is a subject that has received little direct attention. The circumstances under which such a process might take place could conceivably be described as ‘occasional’ under natural conditions and ‘accidental’ under unnatural conditions. A more immediate concern is the ability to detect the presence of vector-independent transmission in action and, where possible, to quantify its contribution to overall infection prevalence. As intrinsically difficult as this process might be, careful observation and the use of laboratory and field-scale experiments have indicated that alternative, vector-independent routes of transmission do exist and might contribute significantly to overall prevalence in some host–vector–pathogen systems.