Retailing in Dublin is now one of the most competitive industries. The city along with other parts of the country has witnessed unprecedented growth over the last decade. With rising income and a rise in general standard of living, customers have more discretionary income to spend. This trend has attracted many big brands in retailing to compete for a piece of the customers spend in Dublin. Marks and Spencer Mary St. is the first store of Marks and Spencer Plc to be established in Ireland in 1981. The store ranks 44th out of the total of more than five hundred stores of Marks and Spencer's Plc worldwide in terms of revenue. Retail revenue of a store is arrived at by multiplying the number of customer footfall converted with the average transaction size. Retailers like Marks and Spencer's as a business growth strategy try and affect both of these variables, i.e. to improve footfall conversion rate and increase average transaction size. This study is aimed at studying the former in terms of establishing the reason for non conversion of customer footfall, in other words to establish the reason for customers visiting the store and not making a purchase. The result of the study would thus be further use in improving the footfall conversion rate of the store and hence directly affecting the top line revenue of the store. The beginning point of the study is the current conversion rate which is approximately 37% and based on this study of the remaining 63% of non converted customers results and subsequent implementation of changes the store aims to achieve an average conversion rate of 42%. The study establishes three broad reasons for customer non conversion at Marks and Spencer's Mary St., Dublin. The first main reason for customer entering the store and not making any purchase is because majority of them are using the store as a thoroughfare. The second reason for non purchase is because the customer did not find the product satisfactory or out of stock which they were looking to buy and the third reason for non conversion being that the customers were generally browsing the store for information for a future purchase. Based on these research results this study recommends changes in merchandise mix to convert the thoroughfaring customers in terms of stocking merchandise which would enable and induce impulse or unplanned purchase. Changes in the store environment pertaining to certain product segments are also recommended based on this study. Also this study highlights the lacunae in the stock and inventory management process of certain foods SKU's and the Womenswear merchandise design, which the customers cited as a reason for non purchase. Overall the aim of this study was to establish micro level reasons for non purchase at the store level and make recommendations which are based on more controllable factors at the store management level and the resource required for implementing the changes are within the control of the store management.