Complement activation pathways with particular attention to lectin pathway were reminded. The current trend is that detailed knowledge of activation triggers and substrates may pave the way to clinical interventions, i.e. inhibition of undesirable excessive activation of complement. Cellular receptors, possible inhibitors of complement cascade, and a list of diseases in which inhibition of complement is needed were shown. C1-inhibitor has its established value in the treatment of hereditary angioedema, but several other inhibitors, like soluble complement receptors, anti-C3 (-C3a), anti-C5 (-C5a) are proposed as therapeutic agents. These inhibitors may be useful in decreasing tissue lesions in such dangerous diseases as eg. Ischemic stroke, myocardial infarct, and septicemia (septic shock).Recently, also mannan binding lectins may be used in therapeutic interventions.