Bubble breakup with permanent obstruction in an asymmetric microfluidic T-junction is investigated experimentally. The breakup process of bubbles can be divided into three stages: squeezing, transition, and pinch-off stages. In the squeezing stage, the thinning of the bubble neck is mainly controlled by the velocity of the fluid flowing into the T-junction, and the increase of the liquid viscosity can promote this process. In the transition stage, the minimum width of bubble neck decreases linearly with time. In the pinch-off stage, the effect of the velocity of the fluid flowing into the T-junction on the thinning of the bubble neck becomes weaker, and the increase of the liquid viscosity would delay this process. The evolution of the minimum width of the bubble neck with the remaining time before the breakup can be scaled by a power-law relationship. The bubble length has little influence on the whole breakup process of bubbles. (c) 2014 American Institute of Chemical Engineers AIChE J, 61: 1081-1091, 2015