SummaryIn a study of 170 haemophilia A patients, 43 were found to have an inhibitory effect; seven had anti-factor VIII inhibitors (a-fVIII) (A), 18 had lupus anticoagulants (LAs) with a strong (B: 12) or weak (C: 6) time-dependent effect and 18 had no time-dependent LAs (D). The a-fVIII showed a neutralizing effect only against factor VIII and negative diluted Russell viper venom time (dRVVT). The LAs were diagnosed by dRVVT; the Staclot® LA agreed with the dRVVT. During the study, three patients changed from an a-fVIII to an LA pattern; they also modified their clinical response.Our prevalence of a-fVIII was low (4%) and we found 21% of LA, with a high (50%) prevalence of time-dependent inhibition. This pattern raises the possibility of the coexistence of LA and a-fVIII, stressing the need to develop specific tests to identify a-fVIII and LA.