diff --git a/mkdocs_include_markdown_plugin/event.py b/mkdocs_include_markdown_plugin/event.py
index f5b08d8..4c0374f 100644
--- a/mkdocs_include_markdown_plugin/event.py
+++ b/mkdocs_include_markdown_plugin/event.py
@@ -16,6 +16,59 @@ TRUE_FALSE_BOOL_STR = {
     False: 'false',
 }
 
+
+def _process_start_end_pairs(text, start_tag, end_tag):
+    """Process start-end tag pairs in the text, extracting content according to rules.
+    
+    - If start_tag is None and end_tag is None: return all text unchanged
+    - If start_tag is None and end_tag is not None: include content before first end_tag, discard end_tag and after
+    - If start_tag is not None and end_tag is None: include content after first start_tag until end of text
+    - If both are specified: process all start-end pairs, extracting content between each pair
+    """
+    if start_tag is None and end_tag is None:
+        return text
+    
+    # Case: only end tag specified - include content before first end tag
+    if start_tag is None and end_tag is not None:
+        end_idx = text.find(end_tag)
+        if end_idx == -1:
+            # No end tag found; include all content
+            return text
+        return text[:end_idx]
+    
+    # Case: only start tag specified - include content after first start tag until end
+    if start_tag is not None and end_tag is None:
+        start_idx = text.find(start_tag)
+        if start_idx == -1:
+            # No start tag found; include nothing
+            return ''
+        return text[start_idx + len(start_tag):]
+    
+    # Case: both start_tag and end_tag specified - process all pairs
+    result_parts = []
+    remaining = text
+    
+    while True:
+        # Find next start tag
+        start_idx = remaining.find(start_tag)
+        if start_idx == -1:
+            # No more start tags; stop processing
+            break
+        remaining = remaining[start_idx + len(start_tag):]
+        
+        # Find end tag after the start tag
+        end_idx = remaining.find(end_tag)
+        if end_idx == -1:
+            # No end tag found after this start; include rest of content
+            result_parts.append(remaining)
+            break
+        # Include content from after start to end tag
+        result_parts.append(remaining[:end_idx])
+        remaining = remaining[end_idx + len(end_tag):]
+    
+    return ''.join(result_parts)
+
+
 INCLUDE_TAG_REGEX = re.compile(
     r'''
         (?P<_includer_indent>[^\S\r\n]*){%
@@ -99,15 +152,18 @@ def get_file_content(markdown, abs_src_path):
                 )
 
         #   string options
+        start = None
+        end = None
         start_match = re.search(ARGUMENT_REGEXES['start'], arguments_string)
         if start_match is not None:
             start = process.interpret_escapes(start_match.group(1))
-            _, _, text_to_include = text_to_include.partition(start)
 
         end_match = re.search(ARGUMENT_REGEXES['end'], arguments_string)
         if end_match is not None:
             end = process.interpret_escapes(end_match.group(1))
-            text_to_include, _, _ = text_to_include.partition(end)
+
+        # Process all start-end pairs
+        text_to_include = _process_start_end_pairs(text_to_include, start, end)
 
         # nested includes
         new_text_to_include = get_file_content(text_to_include, file_path_abs)
@@ -188,13 +244,13 @@ def get_file_content(markdown, abs_src_path):
         start = None
         if start_match is not None:
             start = process.interpret_escapes(start_match.group(1))
-            _, _, text_to_include = text_to_include.partition(start)
 
         end_match = re.search(ARGUMENT_REGEXES['end'], arguments_string)
         end = None
         if end_match is not None:
             end = process.interpret_escapes(end_match.group(1))
-            text_to_include, _, _ = text_to_include.partition(end)
+
+        text_to_include = _process_start_end_pairs(text_to_include, start, end)
 
         # relative URLs rewriting
         if bool_options['rewrite-relative-urls']['value']: