The design and synthesis of water-soluble, synthetic macrocycles as artificial receptors and biomimetic models for enzymes has been a major subject of interest in recent years. Self-assembly of such synthetic receptors with biorelevant molecules is a powerful tool for the understanding, modeling and mimicking of biological systems and developing new materials with specific properties and functions. Along with cyclodextrins, crown ethers and cryptands, calix[n]arenes are one of the most important categories of supramolecular hosts.It is well known that biogenic amines, amino acids, peptides, and proteins constitute one of the most fundamental substrates in biological and artificial processes. The family of calix[n]arenes is deeply involved in molecular recognition of these compounds, especially in the understanding of specific biomolecular interactions which play a key role in modern supramolecular chemistry. Water-soluble calixarenes are of interest in building up systems that mimic natural biological processes through the presence of hydrophobic pockets which can bind nonpolar guests. Moreover, they have also been demonstrated to possess useful potential bio-activities ranging from enzyme inhibition through antithrombotic activity and antiviral activity to antibacterial properties.The aim of this presentation is to summarize the up-to date knowledge about the solid-state interactions of complexes of certain water-soluble calix[n]arenes with biologically relevant molecules. Of the rich chemistry of water-soluble calixarenes that have been synthesized in recent times, the para-sulfonatocalix[n]arenes (n = 4, 6, 8) and diphosphosphonic acid calix[4]arene have been chosen due to their good aqueous solubility, low toxicity, interesting biological activities, and ability to generate a wide range of structural variations in solid state complexes. The presence of anionic groups and a hydrophobic cavity coupled with hydrogen bonding capability makes the anionic calixarenes complementary, in the sense of supramolecular chemistry, to many molecules containing ammonium functions.