diff --git a/ed_lrr_gui/gui/main.py b/ed_lrr_gui/gui/main.py
index afa80e4..c68173e 100644
--- a/ed_lrr_gui/gui/main.py
+++ b/ed_lrr_gui/gui/main.py
@@ -104,6 +104,33 @@ class Job(QObject):
             self.last_val = res
 
 
+class PreprocessJob(Job):
+    def __init__(self, app, main_window, *args, **kwargs):
+        super().__init__(app, main_window, Preprocessor, *args, **kwargs)
+        self.progress_dialog = ProgressDialog("", "Cancel", 0, 0, self.main_window)
+        self.progress_dialog.setAutoClose(False)
+        self.progress_dialog.canceled.connect(self.cancel)
+        self.progress_dialog.show()
+        self.start()
+
+    def handle_progess(self, state):
+        if not self:
+            self.progress_dialog.close()
+            return
+        msg = "Processed: {}/{}".format(
+            sizeof_fmt(state["status"]["done"]), sizeof_fmt(state["status"]["total"])
+        )
+        state["status"]["prc_done"] = (
+            state["status"]["done"] / state["status"]["total"]
+        ) * 100
+        title = "[{prc_done:.2f}%] Processing {file}".format(**state["status"])
+        self.progress_dialog.setMinimum(0)
+        self.progress_dialog.setMaximum(100 * 100)
+        self.progress_dialog.setWindowTitle(title)
+        self.progress_dialog.setLabelText(msg)
+        self.progress_dialog.setValue(int(state["status"]["prc_done"] * 100))
+
+
 class RouterJob(Job):
     def __init__(self, app, main_window, *args, **kwargs):
         super().__init__(app, main_window, Router, *args, **kwargs)
@@ -260,6 +287,17 @@ class ED_LRR(Ui_ED_LRR):
             return callback(fileName)
         return fileName
 
+    def preprocess(self):
+        if self.current_job:
+            # ERROR
+            return
+        bodies_json = self.inp_bodies_pp.currentText()
+        systems_json = self.inp_systems_pp.currentText()
+        output_file = self.inp_out_pp.currentText()
+        self.current_job = PreprocessJob(
+            self.app, self.main_window, systems_json, bodies_json, output_file
+        )
+
     def set_sys_lst(self, path):
         if path not in cfg["history.stars_csv_path"]:
             cfg["history.stars_csv_path"].append(path)
@@ -547,6 +585,7 @@ class ED_LRR(Ui_ED_LRR):
         self.btn_go.clicked.connect(self.compute_route)
         self.btn_add.clicked.connect(self.add_system)
         self.btn_rm.clicked.connect(self.remove_system)
+        self.btn_preprocess.clicked.connect(self.preprocess)
         self.chk_permute.stateChanged.connect(self.update_permute_chk)
         self.btn_out_browse_pp.clicked.connect(
             lambda: self.get_save_file("CSV File (*.csv)", self.set_sys_lst)