This is an attempted scrutiny into various aspects of Arabic-transfer effects upon the English interlanguages of a group of Syrian-Arab adult learners (intermediate to advanced), who are postgraduate students reading for higher degrees in engineering at several universities in Dublin. A multitude of interlingual identifications orally produced by these learners have been collected during a period of eighteen months, and are put forward as the principal focus of this study. By having recourse to both the Standard and Colloquial varieties of Arabic, the areas of language transfer are specified in terms of three linguistic subcomponents: phonology, syntax and semantics (i.e. lexical selection), each categorized within its own taxonomy. Yet, the complexity of the task lies in the tremendous variations Arabic offers between the Standard Variety and the Colloquial Variety at one end, and between the regional dialects of the latter at another. For this reason, such regional dialects are classified into four main dialects constituting Syrian Colloquial Arabic in the sociolinguistic sense. The higher complexity of the task, however, stems from the attempted analysis of specific interlingual identifications which, along the levels of language process and language product, are said to reflect transfer effects from either variety, or from an overlapping existing between the two, or even from a mixture of two or more regional dialects of Syrian Colloquial Arabic. The attested errors made in the domains of phonology and syntax are allocated in terms of two major categories. First, Interlingual Errors are those attested identifications whose analyses seek to establish the potential for Arabic transfer to be the chief source of learning difficulty. Under this category comes a particular type of errors (termed first-language-error negative transfer) which brings to light the learner’s inherent reliance on typical deviation from the Standard Norm of Arabic. Second, Inter-intralingual Errors are those attested identifications which proceed from either an overt combination of Arabic-based transfer (interlingual solution) and English-based transfer (intralingual solution) or a covert interaction between the two sorts of linguistic solution as there is considerable paucity of research into this category. Since most data from transfer-based empirical research, especially those reported from Arab learners of English, concentrate on the negative effects detrimental to the positive effects of first-language influence, this study — besides the investigation of the negative effects of Arabic influence as evidenced by the two major categories of errors — highlights the positive effects which are mostly discernible in the semantic domain of lexical selection. Such polarity is considered by reference to the complementary alliance of contrastive analysis and error analysis, and to current thinking about learner interlanguage and crosslinguistic influence on second-language learning/acquisition. Hence, for each of the three linguistic subcomponents, a provisional hypothesis, in relation to one or both varieties of Arabic, is enunciated to elucidate to what extent the potential for Arabic transfer triggers inhibition and/or facilitation in the learning of English. Throughout the discussion of all the interlingual identifications (actual and predicted) made in a proactive direction as well as some others in a retroactive direction, various tentative suggestions concerning the psycholinguistic processes which incorporate into the transfer mechanism are also adduced to excavate several ’invisible’ areas of Arabic transfer. These underlying processes, which inextricably co-exist in the immanent organization of the human mind, are dealt with in a rather detailed and modified configuration to provide newly endeavoured information on the linguistic behaviour of the Syrian-Arab learner specifically. Therefore, given both the learner’s first language (within its not easily tractable nature) and the key issues connected with language transfer, it is believed that these information are significant on two different but related accounts. First, they raise to the researcher virtually untouched questions of Arabic transfer for more sophisticated theorization about the Arab learner’s entire system in general. Second, they help the teacher, the Arabic-speaking teacher in particular, to utilize his knowledge of Arabic for tackling those transferable spots, and to supplement his teaching plans with more crystallized objectives. This study claims to extrapolate from rather vague schemes a number of interesting, though highly intricate, parameters concerning Arabic transfer, and seems to be one which may contribute to a rewarding exigency for further research.