Engineering design is analyzed in terms of design problem solving. The firs
t two steps of design problem solving, identification of the problem and de
velopment of solution principles, will have die highest impact on the futur
e result and are the most difficult steps. Therefore, possible ways of assi
sting these early steps were analyzed and evaluated in field and experiment
al studies. The main interest was in the interrelationships between mental
problem-solving on the one hand and sketching, physical modelling, and othe
r types of prototyping on the other. Possible ways of assisting in the earl
y steps of engineering design are discussed.