This study examined lead time uncertainties, average inventory and scheduling practice on manufacturing firms in Nigeria. A survey design was adopted, where we identify the population of manufacturing firms and by a purposive sampling procedure, we used twenty (20) manufacturing firms in Port Harcourt, Nigeria. The research instruments used were the questionnaire and oral interview of key personnel in the production, marketing and material management departments. We collected 16 completed questionnaires that give an 80% response rate. The data were analysed in presenting answers to the research questions. We used the statistical tools of the mean, standard deviation, covariance in determining lead time and the weighted mean percentage inventory (WMPI) and weighted mean percentage stock out (WMPS) in determining the inventory profile and the incidence of stock out respectively in both the uniform and fluctuating schedules of product manufacture.From the findings; the calculated WMP1 and the calculated WMPS are higher in fluctuating schedules with 8% and 9% respectively as compared to the low inventory and stock out levels in uniform schedules of calculated WMPI and WMPS of 9% and 6% respectively. Thus production scheduling plays a chief role in improving the overall performance of any company with regards to increased output improved on time delivery and also improved balancing of the production line. Due to the economic view of inventory costs to the overall production activity, we recommend from the results that a uniform production schedule fine tuned to holding a small manageable inventory is preferred. Key Words: Scheduling, Lead Time, Demand Uncertainty, Inventory Management.