- Picture courtesy: Steve Kay -

According to the Japanese with in various blood types, there are certain personality traits that seem to match up with certain blood types.

• TYPE O:  Trendsetter - loyal - passionate - self-confident - independent - ambitious - vain - jealous.  You want to be a leader and when you see something you want you keep striving until you achieve your goal. You are trend-setter, loyal, passionate and self-confident. Your weaknesses include vanity and jealously as well you have a tendency to be competitive.
• TYPE A:   Calm - patient - sensitive - responsible - overcautious - stubborn - unable to relax. You like harmony, peace and organization. You work well with others and are sensitive, patient and affectionate. Your weaknesses are stubbornness and an inability to relax.
  
• TYPE B:   Individualist - dislike custom - strong - optimistic - creative - flexible - wild - unpredictable. You are a rugged individual who is straight forward and likes to do things your own way. Creative and flexible, you adapt easily to any situation. But your instance on being independent can sometimes go too far and become a weakness.
• TYPE AB:   Cool - controlled - rational - sociable - popular - critical - sometimes standoffish - indecisive. Cool and controlled you are generally well like and always put people at ease. You are a natural entertainer who is tactful and fair. But you are standoffish, blunt and have difficulty making decisions.

• A is most compatible with A and AB
• B is most compatible with B and AB
• AB is most compatible with AB, B, A and O
• O is most compatible with O, and AB

Sources:

Blood Types

Personality Traits By Blood Type