The architect Juris Vasiljevs (Yury Vasilyev, 1928-1993) is one of the most renowned specialists of sacred architecture history in Latvia in the second half of the 20th century. Research in the history of architecture is Vasiljevs' central vocation materialised in several dozens of scientific publications and two monographs. This contribution was made possible by the researcher's versatile personality that allowed solving general art-historical questions from the widest variety of aspects and differently from other opinions. The history of theories, hypotheses and conclusions related to research of the sacred architecture in Latvia is rich in successes, surprises and errors. Theoretical schemes devised by historians of art and architecture are in fact completely dependant upon the basic information - the primary source of written evidence and the object itself. It is known that archival records on the oldest monuments are very limited. So a major part of work concerns searches for influences and analogies, assessing the formal traits and the overall background of historical events. Many publications testify to respectable results. Still we should not forget that theories are based on a very flimsy ground - the idea of the architectural object itself. Research of sacred architecture faces objective difficulties conditioned by the specificity of churches. Detailed inspection of the building is largely possible only during major repairs and reconstruction works. These are rarely carried out in churches in comparison with, for instance, dwelling houses. Many generalisations and hypotheses are made after approximate visual inspection whose quality is directly dependant upon the researcher's experience, skill, responsibility and honesty. Incomplete basic information can generate a chain of further misunderstandings and errors. But there are several authors whose work in the phase of initial research has stood the test of time. One of the most prominent figures in the 2nd half of the 20th century is the architect Juris Vasiljevs. Vasiljevs' contribution to the history of Latvian art and architecture is considered several times. He maintained that high-quality research is possible only on the basis of a complex study.