Pronunciation is a very important component of language since verbal aspect of language is more important than its written aspect because of the volume of day to day verbal communication. This basic component of language becomes very important in foreign language learning /teaching because it involves a great deal of conscious learning where there is no native speech community around in most cases. In case of English, it becomes even more crucial due to vocalic richness that it possesses, the lack of correspondence between its actual sounds and its letters of the alphabet and its inherent stress- timed nature. Therefore, both teachers and learners have to be extremely careful in terms of its pronunciation. The present study was conducted to find out correlation between the written and verbal performance of Pakistani learners of English studying at Diploma Level in National University of Modern Languages, Islamabad, Pakistan. Correlation was found in monophthongs (single or pure vowels), diphthongs (double vowels or glides) and lexical stress. The members (both male and female) of the study sample (N=375) hailed from 11 different linguistic backgrounds which include all major languages spoken in the country. The data were collected with the help of two tests: one for written performance and the other for verbal performance. The data were statistically compared in order to determine correlation. The correlation was found with the help of Pearson Product Moment Formula. Though members of the study sample with different linguistic backgrounds exhibited their typical articulatory features, yet results of the study generally indicated strong (in the area of monophthongs), medium (in the area of diphthongs) and weak (in the area of lexical stress) though positive relationship between what the members of the study sample transcribed in phonemic symbols and what they pronounced. As far as the issues of gender and L1 are concerned, the former does not appear to be a crucial factor in terms of articulation whereas the latter does.