A system for aspirating thrombus, comprising: an aspiration catheter comprising: an elongate shaft (700, 818, 900, 915, 934, 950, 1000, 1050, 1200, 1236, 1256, 1276, 1360, 1402, 1440, 1452, 1930, 2018) configured for placement within a blood vessel of a subject; a supply lumen (708, 904, 924, 938, 954, 1004, 1005, 1006, 1206, 1224, 1244, 1264, 1372, 1934, 2093) and an aspiration lumen (160, 710, 902, 922, 936, 952, 1002, 1052, 1204, 1240, 1280, 1366, 1456, 1932, 2032) each extending within the shaft, the supply lumen having a proximal end and a distal end, and the aspiration lumen having a proximal end and an open distal end; and an opening (40, 968, 972, 974, 976, 1234, 1254, 1274, 1296, 2216, 2316, 2436) at or near the distal end of the supply lumen, the opening configured to allow the injection of pressurized fluid into the aspiration lumen at or near the distal end of the aspiration lumen when the pressurized fluid is pumped through the supply lumen; a tubing set (803, 1903, 1904, 2003) comprising tubing and having a distal end configured to couple to the aspiration lumen of the aspiration catheter and a proximal end configured to couple to a vacuum source; a tubing compression element configured to externally engage the tubing of the tubing set at a location between the proximal end of the tubing set and the distal end of the tubing set; and an activation interface configured to activate the tubing compression element to compress the tubing at the location between the proximal end of the tubing set and the distal end of the tubing set; and a pressure sensor (58, 64, 106, 1608, 2006) configured to be in fluid communication with the aspiration lumen of the aspiration catheter and to output a signal indicative of measured pressure, wherein the activation interface is further configured to activate or deactivate a pump configured to pump pressurized fluid through the supply lumen of the aspiration catheter, and wherein an output signal of the pressure sensor is configured to activate or deactivate the pump configured to pump pressurized fluid through the supply lumen of the aspiration catheter. an aspiration catheter comprising: an elongate shaft (700, 818, 900, 915, 934, 950, 1000, 1050, 1200, 1236, 1256, 1276, 1360, 1402, 1440, 1452, 1930, 2018) configured for placement within a blood vessel of a subject; a supply lumen (708, 904, 924, 938, 954, 1004, 1005, 1006, 1206, 1224, 1244, 1264, 1372, 1934, 2093) and an aspiration lumen (160, 710, 902, 922, 936, 952, 1002, 1052, 1204, 1240, 1280, 1366, 1456, 1932, 2032) each extending within the shaft, the supply lumen having a proximal end and a distal end, and the aspiration lumen having a proximal end and an open distal end; and an opening (40, 968, 972, 974, 976, 1234, 1254, 1274, 1296, 2216, 2316, 2436) at or near the distal end of the supply lumen, the opening configured to allow the injection of pressurized fluid into the aspiration lumen at or near the distal end of the aspiration lumen when the pressurized fluid is pumped through the supply lumen; an elongate shaft (700, 818, 900, 915, 934, 950, 1000, 1050, 1200, 1236, 1256, 1276, 1360, 1402, 1440, 1452, 1930, 2018) configured for placement within a blood vessel of a subject; a supply lumen (708, 904, 924, 938, 954, 1004, 1005, 1006, 1206, 1224, 1244, 1264, 1372, 1934, 2093) and an aspiration lumen (160, 710, 902, 922, 936, 952, 1002, 1052, 1204, 1240, 1280, 1366, 1456, 1932, 2032) each extending within the shaft, the supply lumen having a proximal end and a distal end, and the aspiration lumen having a proximal end and an open distal end; and an opening (40, 968, 972, 974, 976, 1234, 1254, 1274, 1296, 2216, 2316, 2436) at or near the distal end of the supply lumen, the opening configured to allow the injection of pressurized fluid into the aspiration lumen at or near the distal end of the aspiration lumen when the pressurized fluid is pumped through the supply lumen; a tubing set (803, 1903, 1904, 2003) comprising tubing and having a distal end configured to couple to the aspiration lumen of the aspiration catheter and a proximal end configured to couple to a vacuum source; a tubing compression element configured to externally engage the tubing of the tubing set at a location between the proximal end of the tubing set and the distal end of the tubing set; and an activation interface configured to activate the tubing compression element to compress the tubing at the location between the proximal end of the tubing set and the distal end of the tubing set; and a pressure sensor (58, 64, 106, 1608, 2006) configured to be in fluid communication with the aspiration lumen of the aspiration catheter and to output a signal indicative of measured pressure, wherein the activation interface is further configured to activate or deactivate a pump configured to pump pressurized fluid through the supply lumen of the aspiration catheter, and wherein an output signal of the pressure sensor is configured to activate or deactivate the pump configured to pump pressurized fluid through the supply lumen of the aspiration catheter.