The main character of the story is Mr. Matthew Bramble, who is known for being a hypochondriac. His nephew, Jerry Melford, describes his uncle:

"Those follies, that move my uncle's spleen, excite my laughter. He is as tender as a man without a skin; who cannot bear the slightest touch without flinching. What tickles another would give him torment; and yet he has what we may call lucid intervals, when he is remarkably facetious—Indeed, I never knew a hypochondriac so apt to be infected with good-humor. . . . A lucky joke, or any ludicrous incident, will set him a-laughing immoderately, even in one of his most gloomy paroxysms . . . " (April 30).

This quote describes how Mr. Bramble is known to be a great worrier, especially about his health. Even so, he also greatly appreciates humor and can be very light-hearted and playful. Therefore, although he can annoy his companions with his constant exaggerated fears and worries, he is a kind person who they genuinely care about.

His nephew, Jerry Melford, writes to his friend Sir Watkins Phillips, a friend from University. His letters are generally much more positive and optimistic than his uncle's. He enjoys seeing new things and meeting new people on their tour. He uses highly intellectual diction choices, as seen in his description of his aunt (Mrs. Tabitha Bramble, Mr. Bramble's sister):

"Mrs. Tabitha Bramble is a maiden of forty-five. In her person, she is tall, raw-boned, awkward, flat-chested, and stooping; her complexion is sallow and freckled; her eyes are not grey, but greenish, like those of a cat, and generally inflamed; her hair is of a sandy, or rather dusty hue; her forehead low; her nose long, sharp, and towards the extremity, always red in cool weather; her lips skinny, her mouth extensive, her teeth straggling and loose, of various colours and conformation; and her long neck shriveled into a thousand wrinkles" (May 6).

In this passage, he describes her unfortunate appearance, using educated word choices such as "complexion," "hue," "inflamed," "straggling," and "conformation." Later, he describes her personality, as well by saying,

"In her temper, she is proud, stiff, vain, imperious, prying, malicious, greedy, and uncharitable. In all likelihood, her natural austerity has been soured by disappointment in love; for her long celibacy is by no means owing to her dislike of matrimony" (May 6).

Here, her nephew explains how she is an extremely unpleasant character to be around. He supposes that this must be because nobody wanted to marry her, though she'd tried to marry many people. He suggests that she might have bitterness and frustration about this. (She is one of the characters who is most upset by Humphry Clinker's partial nakedness, when she meets him later in the story. This is because she tries to present herself as a very pure and proper lady.)

Another significant character is Jerry's sister, Lydia Melford. She is very interested in style, fashion, upper class society, and young men. While in Bath, she writes to her friend about the entertainments:

"Hard by the Pump-room, is a coffee-house for the ladies; but my aunt says, young girls are not admitted, inasmuch as the conversation turns upon politics, scandal, philosophy, and other subjects above our capacity; but we are allowed to accompany them to the booksellers shops, which are charming places of resort; where we read novels, plays, pamphlets, and news-papers, for so small a subscription as a crown a quarter" (April 26).

She discusses the places she is allowed to visit in Bath and which places are seen as improper for a young...