Serological tests for Borrelia burgdorferi were carried out in a series of 27 patients with primary antiphospholipid syndrome (PAPLS). The results showed a 14% prevalence of false positive Lyme disease serology in this patient population. In patients with PAPLS and false positive serologic tests for Borrelia burgdorferi neurological involvement was significantly more common (p = 0.012, Fisher's exact test) than in patients with PAPLS without that finding. We insist on the possibility that patients with PAPLS may have false positive serological tests for Borrelia burgdorferi as measured by IFI with the resulting diagnostic error. In these cases, confirmation by other techniques such as ELISA or immunoblotting is recommended.