What are the factors and how important are they for the development and improvement of lexical English skills among teachers in training? With strong lexical (vocabulary) knowledge in English, teachers develop their communicative competence, which is an essential prerequisite for conducting effective classroom instruction. Communicative competence is what teachers need to facilitate learning effectively. Therefore, it is of great importance that teachers possess a strong and functional English vocabulary that is developed in the years prior to their service. This book highlights the factors that contribute to teachers acquiring lexical English skills before their service. It presents the current state of vocabulary knowledge among teachers in training across the Isabela State University campus, a leading educational institution in Northern Luzon, Philippines.