The peptide performing best in our investigation was longD8-9, a 42mer peptide deriving from E. multilocularis antigen B8/1. It reached a sensitivity of 57% and a specificity of 94%. The reactivity of LSP longD8-9 with sera from AE as well as CE patients suggests its use for both, patient screening as well as for follow-up examinations of treated patients. For the latter purpose, it will be necessary to determine the proportion of patients seroconverting during treatment. The applicability of our peptide antigen for monitoring treatment follow-up samples is ongoing work in our laboratory. Table 3 . Numbers of sera tested positive with peptides longD12, longD1 and longD8-9. Our results confirm previous reports [38, 41] that a test based on a single peptide needs to be complemented by additional peptides to reach a sensitivity comparable to the antigen extract. To compensate for limited sensitivity of individual peptides, we performed ELISAs with combinations of synthetic peptides applied as mixtures for coating. We compared these results to the ''cumulative sensitivity'', a theoretical value obtained by summing up the positive results from individual peptide ELISAs for each serum tested. The cumulative result amounted to a theoretical sensitivity of 70%. We did not detect this high sensitivity. In contrast, pooling of 3 peptides in one well led to a loss of positive signals otherwise obtained with individually tested peptides. 8/29 echinococcosis samples were lost through pooling. One reason was suggested by an increased cut-off for pooled peptides. In some sera similar ODs were observed in individual test and in peptides mixtures, but due to increased cut-off for pooled peptides, these sera turned negative. The loss of sensitivity obtained with pooled peptides in mixW could also be due to partial occupation of streptavidin binding sites with less reactive antigen. The same reasons may account for increased specificity. Combination of peptides in one well led to a loss of unwanted cross-reactivity with 5/11 previously false positive signals disappearing. Thus in our study, pooling peptides increased specificity, but lowered sensitivity. In future work peptide mixes might be optimized by combining peptides with equally good diagnostic sensitivity and specificity. In particular, the sensitivity of mixes is likely increased by continuous search for new peptides with improved diagnostic operating characteristics as substitutes for the least reactive candidates. The behaviour of peptide mixtures applied as antigens in ELISA needs further investigation.