From childhood, Leite de Vasconcelos was attentive to his surroundings, recording in small notebooks everything that interested him. At the age of 18 he went to Porto, where in 1881 he completed a degree in natural sciences and, in 1886, a second degree in medicine. However, he practiced as a physician for only one year, serving as a health care administrator in Cadaval during 1887.
Early in his career, Leite de Vasconcelos turned his attention to the Galician language. In 1902 he published an article in the journal Revista Lusitana, based on a manuscript entered into the National Library of Madrid sometime after 1843. In his Esquisse d’une Dialectologie Portugaise he characterized Galician as a co-dialect of Portuguese: rather than having arisen from Portuguese, Galician had developed as a related but distinct branch of the same Galician-Portuguese trunk. In 1910 Miuçalhas gallegas was published; drawing attention to various aspects of Galician studies, it contained a brief discourse on the linguistic boundary between Fala and Galician, corresponding to Ribadavia, :gl:Ferreiros, Entrimo, Entrimo|Ferreiros and San Miguel de Lobios in Ourense, much of Hermisende and Zamora—although the last of these is, strictly speaking, a separated or transmontane Fala. Leite was somewhat hasty in collecting his Galician data; in most cases he spent only one day on his visits to Galicia, a marked contrast to the diverse data he had amassed on other Galician-Portuguese dialects. Despite his enormous talent and immense capacity for scholarship, perhaps he spent too much time on his other research and writing to avoid pitfalls on his Galician work. At the dawn of the 20th century a golden opportunity was lost, therefore, of applying the scientific precision of historical linguistics, in the hands of an authentic philologist, to the analysis of the Galician language.
On his death at 82 he bequeathed to the Museu Nacional de Arqueologia his library of about 8,000 titles, as well as manuscripts, correspondence, engravings and photographs.
Works
O Dialecto Mirandez
Portugal Pré-histórico
A Evolução da Linguagem
Revista Lusitana
Religiões da Lusitânia
Estudos de Filologia Mirandesa
Esquisse d’une Dialectologie Portugaise
Textos Archaicos
Livro de Esopo
O Doutor Storck and A Litteratura Portuguesa
Lições de Philologia Portuguesa
História do Museu Etnológico Português
Signum Salomonis
De Terra em Terra
De Campolide a Melrose
Mês de Sonho
A barba em Portugal
A figa
Antroponímia Portuguesa
Opúsculos
Etnografia Portuguesa
Filologia Barranquenha – apontamentos para o seu estudo