Allocation concealment is defined as the procedure for protecting the randomisation process so that the treatment to be allocated is not known before the patient enters into the study. Hiding the allocationsequence from those performing randomization is known as “Allocation Concealment”. The primary purpose of randomizing patients into treatment arms is to prevent researchers, clinicians and patients from predicting and thus influencing, upcoming group assignments. Allocation concealment is a strict implementation of the schedule must be secured through an assignment mechanism that prevents biases that could stem from foreknowledge of treatment assignment. Enclosing assignments in sequentially numbered, opaque, sealed envelopes can be a good allocation concealment mechanism if it is developed and onitored diligently. Unpredictability is assured through the process of concealment which is critical in preventing selection bias that is the potential for investigators to manipulate who gets what treatment such manipulation in clinical trials has been well documented. Unclearly concealed and inadequately concealed trials compared to adequately concealed trials, exaggerated the estimates of an intervention’s effectiveness by 30% to 40%, on average. Finally note that the issues of randomization and concealment should be kept separate from blinding and they are completely different. 

Keywords: Randomization; Allocation concealment; Sequentially numbered opaque sealed envelopes; Nurse researcher.