As longer, full well-stream flowlines are utilized to reduce the costs of deepwater and satellite developments, routine production monitoring attains a new level of importance. Of particular interest is the operational impact that blocking agents such, as paraffins, asphaltenes, hydrates, and scale can have on the flowlines. Because blockages can reduce and even disrupt production monitoring flowline performance becomes an economic necessity. This paper considers the application of the backpressure technique as a means of monitoring the growth of blockages in gas flowlines. Using only routine production data, this method quantifies partial blockages by comparing production data to a baseline performance curve. Experimental verification was performed using the LSU 9460-ft flowloop of 4 1/2-in. drillpipe. Multirate tests were conducted using methane at 250-620 psig with partial blockages placed in the flowloop. Good agreement with the backpressure model was observed.